Air Quality: Health Standards for Abrasive Blasting and Drill Dust Control;

SUMMARY: This final rule addresses abrasive blasting and drill dust

control at all metal and nonmetal and coal mines. The final rule

retains existing requirements for rock drilling operations at metal and

nonmetal mines and establishes new requirements for rock drilling

operations at surface coal mines and surface work areas of underground

coal mines. The final rule also revises existing requirements for rock

drilling operations at underground coal mines. In addition, it

establishes new specific standards for abrasive blasting operations at

coal mines and expands existing provisions at metal and nonmetal mines.

EFFECTIVE DATE: April 19, 1994.

FOR FURTHER INFORMATION CONTACT: Patricia W. Silvey; Director, Office

of Standards, Regulations and Variances; MSHA; (703) 235-1910.

SUPPLEMENTARY INFORMATION:

I. Background

On August 29, 1989 (54 FR 35760), MSHA published a notice in the

Federal Register inviting public comment on a proposed rule on air

quality, chemical substances, and respiratory protection in mining. The

proposed rule addressed means of controlling exposure to hazardous

substances, permissible exposure limits, exposure monitoring, dangerous

atmospheres, respiratory protection, carcinogens, asbestos construction

work, drill dust control, abrasive blasting, and prohibited areas for

food and beverages. This final rule addresses abrasive blasting and

drill dust control, which are the first of these sections to be

completed.

In comments on the proposal, the Agency received requests to hold

public hearings. In response, the Agency held three sets of public

hearings on the proposed rule. The first set of public hearings, which

specifically addressed abrasive blasting and drill dust control, was

held in Denver, Colorado, on June 4, 1990, and in Pittsburgh,

Pennsylvania, on June 7, 1990. Following the public hearings, the

record remained open until August 30, 1991, to allow interested persons

to submit supplementary statements and data.

During the rulemaking process, MSHA received written and oral

comments from all segments of the mining community. The Agency's final

rule addresses the comments received and is consistent with the goals

of the Federal Mine Safety and Health Act of 1977 (Mine Act), Executive

Order 12866, the Regulatory Flexibility Act, and the Paperwork

Reduction Act.

After analyzing the comments received, the public hearing

testimony, and technical and health data, the Agency is issuing this

final rule on abrasive blasting and drill dust control to address

immediate health concerns. The final rule makes no substantive changes

to existing regulations for drill dust control at metal and nonmetal

mines and at underground coal mines. However, the final rule

establishes new requirements for drill dust control at surface coal

mines. The final rule also expands existing requirements for abrasive

blasting at metal and nonmetal mines and establishes new requirements

for both surface and underground coal mines. The existing respirable

coal mine dust standards in parts 70, 71, and 90 are unaffected by this

final rule.

This final rule is consistent with section 101(a)(6)(A) of the Mine

Act, which mandates the development of standards dealing with toxic

substances to attain the highest degree of protection possible for

miners. Section 101(a)(6)(A) also requires MSHA to take into

consideration the latest available scientific data in the field, the

feasibility of the standards, and experience gained under the Mine Act

and other health and safety laws.

This rulemaking codifies health standards for abrasive blasting and

drill dust control in a new part 58 for metal and nonmetal mines and a

new part 72 for coal mines. In the following discussion, the

designation ``58/72'' indicates that a standard appears in both parts

58 and 72.

In an effort to fully explore the issues presented by this

rulemaking, MSHA has included in the rulemaking record several

scientific studies concerning abrasive blasting and drill dust control

that were published after the close of the comment period on August 30,

1991. These references are CDC/NIOSH Alert * * * Lead Poisoning in

Construction Workers, April 1992; CDC/NIOSH Alert * * * Silicosis and

Deaths in Rock Drillers, August 1992; CDC/NIOSH Alert * * * Silicosis

and Deaths From Sandblasting, August 1992; Goodman et al., 1992; and

Mickelsen and Froehlich, May 1993. None of these references are

entirely new data, but rather they further confirm the Agency's

rulemaking decision and address concerns raised by commenters. MSHA

reviewed these documents in order to attain its statutory obligation to

consider the latest available scientific data in the field.

II. General Introduction

Whenever miners conduct abrasive blasting or drilling they are

exposed to serious health hazards that require implementation of

specific dust controls before engaging in the activity. Enforcement by

using the permissible exposure limits alone would provide inadequate

protection for miners in these activities. During abrasive blasting and

drilling, there is the potential for extremely high exposures in short

periods of time to both the miners doing the abrasive blasting or

drilling and to other miners in the immediate area. Relying on samples

could allow miners to receive extremely hazardous doses of contaminants

before sampling results could be analyzed. In addition, miners could

face rapidly changing environments, all having potential for high

exposure. In addition, during abrasive blasting, although the type of

abrasive material may remain constant, the coatings of the base

material and the accumulated contaminants in the recycled abrasive

material may cause exposure to vary widely (Rekus, 1988; Mickelsen and

Froehlich, 1993).

Administrative controls, which control exposures by limiting the

amount of time a miner is in a contaminated atmosphere, are not

appropriate for abrasive blasting and drilling operations. Inherent in

the effective use of administrative controls is the assumption that the

environmental exposure will remain constant or predictable. This is not

characteristic of these two operations.

Due to the nature of the work being performed, the location of

these activities can change rapidly. The frequent change of location

also can make it extremely difficult to get sampling results quickly

enough to effectively evaluate a miner's current exposure. This is

particularly true in the case of independent contractors who, by the

time sampling results are evaluated, may have moved to another location

or mine. There also exists the problem of maintaining sample integrity

during abrasive blasting operations. When sampling is done outside of

an abrasive blasting hood, high velocity rebounding or ricocheting

abrasive material from the blasted surface can destroy the sample.

Because of these factors, the final rule specifies engineering

controls for drill dust control at all mines and requires a totally

enclosed system or an abrasive blasting respirator during abrasive

blasting operations.

Exposure to silica is a significant health hazard in abrasive

blasting and in drilling. When workers inhale silica, the lungs react

by developing fibrotic nodules and scarring around the trapped silica

particles. This condition is known as silicosis and can result in

respiratory difficulty and eventually death. Symptoms associated with

silicosis include shortness of breath, fever, and cyanosis. Severe

fungal or mycobacterial infections, such as tuberculosis, often cause

complications and may be fatal. Dust-impaired macrophages can no longer

function effectively in fighting disease by killing mycobacteria and

other organisms.

It is generally believed that the silica dust overwhelms

macrophages in the lungs (Craighead et al., 1988). This can be due to

silica toxicity or to a combination of toxicity and dust overload

(Morrow, 1988; Claypool, 1988; Berkow, 1987). When a person is exposed

to respirable dust containing crystalline silica, three types of

silicosis may occur, depending on the dust concentration. Chronic

silicosis usually occurs following relatively low exposures over 10 or

more years. Accelerated silicosis results from exposure to high

concentrations over 5 to 10 years. Acute silicosis or silico-

proteinosis occurs from exposure to the highest concentrations, with

symptoms developing within a few weeks to 4 or 5 years from initial

exposure (Merchant, 1986). Acute silicosis is characterized by the

accumulation of an amorphous granular lipoprotein released into the air

spaces and rapid development of respiratory disability in a few years

(Vallyathan, 1988). Silico-proteinosis results from dust overload as

well as silica toxicity (Claypool, 1988; Morrow, 1988; Heppleston et

al., 1970; Rubin et al., 1980).

When particles impact a surface during abrasive blasting, they

typically fracture into finer particles and become airborne. Inhalation

of freshly fractured silica particles appears to produce a more severe

lung reaction. Vallyathan (1988) studied freshly fractured silica dust

and found it exhibited more toxic characteristics than silica that had

aged at least 30 hours. Freshly fractured silica can react with water

to release short-lived oxygenated free radicals. Alveolar macrophages

are stimulated to a greater extent by freshly fractured free silica

than silica that has been aged. Vallyathan theorizes that this freshly

fractured silica and macrophage interaction may contribute to

development of acute silicosis, which is associated with sandblasting,

rock drilling, tunnelling, and silica flour mill operations.

III. Abrasive Blasting

A. Introduction

Abrasive blasting is the technique of projecting particles to

remove paint or other unwanted substances from a surface for the

purpose of preparing it for painting, welding, or other activities. In

mining, the location and type of equipment being cleaned by abrasive

blasting may change during every operation. The abrasive material can

be composed of a single substance, such as silica, or a composite

material, such as slag. The abrasive material, as well as anything

removed from the object or surface, can become airborne. In some

instances, the abrasive material can be collected and reused. This

process has the potential for accumulation of various toxic substances,

such as lead from paint (Rekus, 1988; CDC/NIOSH Alert, April 1992;

Mickelsen and Froehlich, 1993). The exposure hazard associated with

abrasive blasting is dependent on the type of abrasive blasting

conducted, the type of abrasive material used, and the substance being

abraded. Abrasive blasting represents a unique situation in mining that

is difficult to control by using traditional means.

There are several different methods of abrasive blasting. Air

pressure blasting is the most commonly used technique in mining. In

this process, air pressure is used to propel abrasive material at a

high velocity against an object to abrade unwanted substances from its

surface. This type of abrasive blasting has the greatest potential to

cause overexposure to toxic substances resulting from the abrasive

material itself or the substances removed.

Another abrasive blasting method uses abrasive material entrained

in water or other liquid media. The abrasive material is propelled by

either liquid pressure or a combination of liquid and air pressure. The

abrasive material entrained in the liquid media is forced to strike an

object at a high velocity, which causes unwanted substances to be

abraded. Though the potential for overexposure is reduced by the water

used in this method, a health hazard still exists due to small

fractured particles found in the mist that is generated. After

blasting, cleanup of dried materials also can be a potential exposure

problem (Craighead et al., 1988).

In mining, abrasive blasting is a commonly used method of cleaning

surfaces in preparation for painting or welding. It is generally done

on a periodic basis, most commonly during maintenance procedures and

plant overhaul. For these activities, the hazards of abrasive blasting

in mining are the same as those in general industry. The references

cited in this preamble generally relate to studies conducted on non-

miners. Documentation of similar disease prevalence in miners

performing abrasive blasting is limited because miners who perform

abrasive blasting are grouped into maintenance or general laborer job

categories and, thus, are often difficult to identify. Also, many mine

operators employ independent contractors to perform these activities,

and disease prevalence among such contractors is difficult to track.

Because the process and materials are essentially the same in mining as

in general industry, MSHA believes that miners performing abrasive

blasting experience risks similar to those described in the scientific

studies cited in this preamble that address industries other than

mining.

B. Background

1. Metal and Nonmetal Mining

Existing metal and nonmetal standards at 30 CFR 56/57.5010 prohibit

the use of silica sand or other materials containing more than 1

percent free silica as an abrasive material in abrasive blasting at all

surface mines and at the surface areas of underground mines, unless all

exposed persons are protected by a full-flow respirator or equivalent.

Existing Sec. 57.5016 prohibits the use of silica sand or other

materials containing more than 1 percent free silica as an abrasive

substance in abrasive blasting operations underground.

The majority of abrasive blasting performed at metal and nonmetal

mines is conducted on the surface and most of these operations are

carried out by hand-held dry blasting methods. In almost all of these

operations, abrasive blasting hoods with supplied air are used to

protect the worker. These hoods are approved by the National Institute

for Occupational Safety and Health (NIOSH). Also, small abrasive

blasting work boxes are used in some maintenance shops.

2. Coal Mining

Currently, MSHA does not specifically regulate abrasive blasting at

surface and underground coal mines. However, 30 CFR 75.1720 and 77.1710

require protective clothing for protection against the impact of

particles from such operations at coal mines. Abrasive blasting occurs

at a small number of surface and underground coal mines and then only

on an infrequent basis. These operations may be performed by either the

mine operator or an independent contractor. MSHA has observed abrasive

blasting at coal mines where adequate respiratory protection was not

being worn. Due to the serious health risk of overexposure to

crystalline silica and other materials being used, the final rule

requires the use of engineering controls or personal protective

equipment at all abrasive blasting operations.

C. Abrasive Blasting--Toxicity

For many years, abrasive blasters have been considered to be at

high risk of developing silicosis (Craighead et al., 1988). The use of

sandblasting for the purpose of cleaning metal surfaces before painting

has been prohibited by law in the United Kingdom since 1949 and in the

European Economic Community since 1966 (Ziskind, 1976). The increased

use of sand as an abrasive in the United States since World War II was

noted to have produced a resurgence of accelerated silicosis in

sandblasters (Ziskind, 1976). In 1974, NIOSH recommended that silica

(or other substances containing more than 1 percent free silica) be

prohibited as an abrasive blasting material (NIOSH, 1974).

Early reports of acute silicosis among sandblasters include

Buechner and Ansari (1969), who reported evidence of an alveolar

proteinosis-like response of pulmonary tissue to occupational silica

exposure. Autopsy examination of four sandblasters revealed silica

crystals and a protein material in the lungs. The workers had

sandblasted for an average period of 4 years.

Abrasive blasters are also at high risk of developing active

tuberculosis (Bailey et al., 1974). Merewether (1936) found that the

average duration of employment at the time of death was 8.3 years for

abrasive blasters with silico-tuberculosis, compared to 32 years for

this fatal combination in other occupations. Bailey et al. (1974) also

found similar results. Merewether (1936) reported that 5.4 percent (24

of 441) of the sandblasters in his study in Great Britain died from

silicosis or silicosis with tuberculosis in a 3.5-year period.

In 1988, a physician reported three cases of silicosis in

sandblasters (CDC MMWR, 1990). One of these individuals, a 34-year-old

man, died with acute silicotic alveolar proteinosis. Later

investigations revealed an additional seven sandblasters who had

silicosis. All worked at one facility that used a mixture of flint and

garnet to sandblast oil pipe. The mean duration of exposure was 4.5

years, with one case as short as 18 months. Blast cabinets and

protective booths were poorly designed and not maintained. Workers wore

only disposable respirators and none had been fit tested.

In another case, a 49-year-old nonsmoker with a 6-year history as a

sandblaster was admitted to a hospital complaining of difficulty in

breathing, cough, lack of appetite, fever and a 20-lb weight loss

(Owens et al., 1988). He was diagnosed with chronic silicosis and

bacterial pneumonia and died on the twentieth day of his hospital stay.

Four sandblasters in a tombstone factory developed acute silicosis

after an average of 3-years' exposure at ages 23, 37, 38, and 47

(Suratt et al., 1977). Three of the four are known to have died from

silicosis. It was determined that the blasting agent used during

sandblasting contained 98 percent crystalline free silica. The

employees worked inside enclosed but vented blasting chambers and wore

negative pressure half-mask respirators with disposable filters.

Bailey et al. (1974) examined the records of 88 sandblaster-

painters who were admitted to Charity Hospital in New Orleans. Of

these, 83 had silicosis and 22 were confirmed as having tuberculosis.

The mean age of these 22 individuals was 44, with an average exposure

of 10 years. At the time of the study, 27 percent (8 of 22) had died.

Three of these individuals died of ``acute'' silicosis, which had

characteristics of pulmonary alveolar proteinosis. The average age at

the time of death was 44.2 years, with an average exposure of 8.3

years. The authors note that in almost all of the 22 cases, the

sandblaster hoods were not attached to an external air supply.

Samimi et al. (1974) studied sandblasting and associated workers on

steel fabrication yards. They sampled sandblasters and workers

physically located near the abrasive blasting operations. Personal

exposure of helpers, pot handlers, painters, and welders indicated an

average exposure from 1.9 to 7.4 times the permissible threshold limit

value (TLV), with the helper having the highest exposure among the

secondary occupations. Environmental samples on the outside of abrasive

blasting hoods were as high as 37.25 mg/m\3\, which was 318 times the

TLV. Samples taken inside non-supplied-air abrasive blasting hoods

exceeded the TLV in all cases, with the highest exposure being 80 times

the TLV. Although sampling data indicated that overexposures occurred

with supplied-air respirators being used, the authors noted that this

may have been due to sampling during times when the respirator was not

continually worn, as well as to poorly maintained equipment. Samples

taken under modern and well-maintained hoods indicate exposures would

be only one-third of the TLV.

In studies, other abrasives used instead of silica also have been

demonstrated to be fibrogenic. MacKay et al. (1980) found that

commercial coal-slag derived grit produced pulmonary fibrosis in rats.

The copper slag tested did not produce fibrosis, but did produce

granulomas.

Stettler et al. (1988) studied the fibrogenic and carcinogenic

potential of copper and nickel smelter slags that have been used as a

substitute for sand in abrasive blasting. The copper slags not only

produced some fibrosis, but also produced lung tumors in the rats. The

authors were unable to determine the exact causative agent because many

trace elements, such as arsenic and beryllium, were present in the

slags.

D. Control Technology

Abrasive blasting creates high particulate concentrations within

open or enclosed spaces where the work is performed. The force of the

abrasive stream (60 to 120 pounds per square inch (psi)) produces fine

fragments of respirable size (less than 10 micrometers (m) in

diameter). A high percentage of the particles are in the 1 to 3

m range in which alveolar deposition is significant (Bailey et

al., 1974).

MSHA recognizes that there are limitations in the engineering

controls for abrasive blasting in mining. Abrasive blasting, by its

nature, is used to prepare equipment for maintenance. Because the

equipment to be prepared can vary considerably in size and location at

the mine, it would be extremely costly and technically very difficult

to build temporary enclosures around the equipment with properly

designed ventilation and dust filtration equipment to prevent exposure

to miners. Some small equipment can be easily moved, which allows for

abrasive blasting of that equipment to be performed in commercially

available boxes, cabinets, or blasting rooms. Blast cleaning cabinets

are used to clean relatively small objects that can be manipulated by

hand. When using blasting cabinets, the operator stands outside of the

enclosed cabinet and uses a set of attached gloves or remote controls

to perform the blasting operation inside the enclosure. The blasting

media is maintained inside the enclosed cabinet by negative pressure.

When operators use a properly designed and maintained blasting cabinet,

exposure to hazardous material is minimal.

The majority of abrasive blasting in mining is done on large

equipment at varied locations on the mine site. In these cases, the

primary means of controlling exposure is the NIOSH-approved abrasive

blasting hood. This hood has the advantage of providing safety

protection from the impact of projected particles, as well as

respiratory protection from toxic materials.

E. Summary and Explanation of Rule

Paragraph (a) of Secs. 58/72.610 is derived from existing Secs. 56/

57.5010 for metal and nonmetal mines. Sections 56/57.5010 prohibit the

use of materials containing more than 1 percent free silica as an

abrasive substance in abrasive blasting operations at surface areas of

metal and nonmetal mines, unless all exposed persons are protected with

full-flow respirators or equivalent. Under the final rule, when an

abrasive blasting operation is performed, all exposed miners must

properly use respirators approved for abrasive blasting by NIOSH or the

operation must be done in a totally enclosed device.

A commenter to the proposed rule recommended that MSHA require

supplied-air respirators at surface mines, unless the work being

performed was in a totally enclosed device with the operator outside

the device. This commenter stated that eliminating silica-containing

materials from abrasive blasting will not necessarily eliminate the

associated health hazards, because animal experiments with other

abrasive substitutes have produced fibrosis or scarring of the lungs.

In addition, NIOSH recommended that abrasive blasting respirators be

used whenever there is detectable silica in the abrasive blasting

material, even when it constitutes less than 1 percent.

MSHA agrees with the commenter that other abrasive materials can

present a health hazard in abrasive blasting. The final rule,

therefore, expands the scope of the proposed rule to address these

hazards by requiring respirators approved for abrasive blasting to be

used when abrasive blasting is conducted, unless the work is performed

in a totally enclosed device with the operator outside the device.

Abrasive blasting respirators will also provide the necessary safety

protection because they are designed to protect the wearer's head and

neck against impact and abrasion from rebounding material, as well as

provide respiratory protection. The impact of high-velocity rebounding

or ricocheting abrasive material from the blasted surface can penetrate

other types of personal protective equipment.

Existing metal and nonmetal Secs. 56/57.5010 require the use of

``full-flow respiratory protection or equivalent'' when using abrasives

containing more than 1 percent free silica. ``Full-flow'' is an

outdated term referring to a respirator that had a flow of air

mechanically forced into the facepiece, as opposed to a negative-

pressure respirator that requires inhalation by the wearer to bring air

through the filter into the facepiece. A ``full-flow'' respirator does

not easily correspond to current NIOSH certification of respiratory

protection. The proposed rule replaced ``full-flow respiratory

protection or equivalent'' with ``supplied-air respirator approved for

abrasive blasting'' which required NIOSH approval for that use.

Since the publication of the proposed rule, powered air-purifying

respirators have received NIOSH approval for use in abrasive blasting

operations. Powered air-purifying respirators approved by NIOSH for

abrasive blasting would meet the current standard of ``full-flow

respiratory protection or equivalent.'' Therefore, MSHA is deleting the

words ``supplied-air'' in the final rule to permit the use of any

respirator approved by NIOSH for abrasive blasting. This will not

result in any diminution of safety for the miner, but will permit the

use of any new respiratory protection that has been approved by NIOSH

for abrasive blasting operations.

NIOSH recommended banning the use of any product containing more

than 1 percent free silica as an abrasive substance at all mines. They

also recommended banning the use underground of any product that

contained any detectable silica, including those containing less than 1

percent. NIOSH suggested that at surface operations where abrasive

blasting products containing any detectable silica up to 1 percent are

used, MSHA should require the use of abrasive blasting respirators.

In the preamble to the proposed rule, MSHA used the terms

``quartz'' and ``free silica'' interchangeably in the discussion on

abrasive blasting, although the term ``1 percent quartz'' was used in

the proposed rule itself. NIOSH in its comments expressed concern about

the proposed exemption of material containing ``1 percent free silica

or less.'' In the final rule, MSHA is using ``1 percent free silica''

which is consistent with the wording of the current metal and nonmetal

standard and is the term used by NIOSH.

MSHA disagrees with the suggestion that substances containing more

than 1 percent free silica be banned at surface locations. Adequate

protection will be provided to miners with the requirement that miners

exposed to abrasive blasting use respirators approved for abrasive

blasting or the operation be conducted in totally enclosed devices.

Several types of abrasive blasting enclosures are commercially

available and can be used successfully to control exposure to all

contaminants, not just silica. Alternatively, abrasive blasting

respirators also offer protection against all contaminants, including

silica. As a result, the final rule does not ban the use of abrasive

blasting materials containing silica at surface operations.

One commenter recommended monitoring of the environment when

abrasive blasting products containing less than 1 percent free silica

are used. This commenter suggested that abrasive blasting respirators

or engineering controls be required if the level of exposure to

respirable quartz dust at surface operations exceeds 50 g/

m\3\. The requirement in the final rule requiring enclosure or abrasive

blasting respirators affords more protection to the miners.

Other commenters recommended that the proposed section on abrasive

blasting be deleted and that an exposure limit for silica sand govern

the exposure during abrasive blasting operations. Because of factors

previously discussed, specifying controls is necessary. Generally, it

is not practical to conduct monitoring in an abrasive blasting zone

because the sampling device could be destroyed or damaged by rebounding

material. In addition, because of the wide variability in blasting

operations, sampling is often inadequate as a means of assessing the

miners' exposures. The safety hazard associated with abrasive blasting

is such that hoods or enclosures are necessary to ensure better

protection for miners engaged in abrasive blasting activities.

Paragraph (b) of Secs. 58/72.610 is derived from existing metal and

nonmetal Sec. 57.5016 and prohibits the use of silica sand or other

materials containing more than 1 percent free silica as an abrasive

substance in abrasive blasting at underground mines. Currently, MSHA

does not explicitly regulate abrasive blasting underground at coal

mines. However, Sec. 75.1720 requires protective clothing for

protection against the impact of particles from such operations. NIOSH

and the majority of commenters recommended that abrasive blasting

materials containing more than 1 percent free silica be banned

underground. MSHA agrees because airborne respirable silica could be

carried from an abrasive blasting operation throughout the mine by the

ventilation system, thus exposing unprotected miners. In addition,

there are substitute abrasives that have been used effectively for this

type of work underground. Accordingly, the Agency has retained the

provision from the proposed rule which would ban the use underground of

abrasive blasting materials containing more than 1 percent free silica.

Because Secs. 58/72.500, respiratory protection, of the proposed

Air Quality standard have not been promulgated, MSHA uses the term

``properly used'' and ``approved by NIOSH'' in Sec. 72.610(a) to assure

protection. Section 58.610 refers to Secs. 56/57.5005 to assure

continued proper use of respiratory protection. When the respiratory

protection provisions of the Air Quality rulemaking are promulgated,

Secs. 58/72.610 will be modified to refer to that section.

IV. Drill Dust Control

A. Introduction

Drilling operations have long been recognized as causing

respiratory hazards in mining. Most rock drilling produces respirable,

silica-bearing dust that can cause silicosis and alveolar proteinosis.

All types of silicosis have been documented in drillers. In 1958, the

Public Health Service, in conjunction with the Bureau of Mines, issued

a report on silicosis in metal and nonmetal mining that identified

drilling as one of the most prolific dust-producing operations. In

August 1992, the CDC/NIOSH of the Public Health Service again

reemphasized its earlier warnings on silicosis occurring in rock

drillers. In this Alert, NIOSH described 23 cases of silicosis

occurring in rock drillers, including 11 rock drillers in coal mines.

MSHA believes that control of drill dust also will prevent the

development of pulmonary alveolar proteinosis, as well as a mixed dust

fibrosis and silico-proteinosis.

MSHA has recognized the health hazard presented by drilling in

underground coal mining and that surface coal mines also need the

additional protection set forth in this final rule. In metal and

nonmetal mines under existing regulations over the past 13 years, MSHA

had three reports of pneumoconiosis in rock drillers and two cases in

driller helpers. Over the past 10 years, there were 30 cases of

pneumoconiosis reported to MSHA in highwall drill operators and helpers

at surface coal mines.

In addition, Banks (1983) identified three cases of acute silicosis

in coal miners. Parker et al. (1989) identified nine cases of silicosis

in surface miners in a 10-year period in West Virginia. The median age

of the miners was 35 years. All were drillers, driller helpers, or

supervisors with a median of 6 years above-ground exposure. Four were

nonsmokers. Two had acute silicosis, one of whom died within 2 years of

diagnosis. Five had accelerated silicosis, one of whom had silico-

tuberculosis. Two with longer periods of exposure were diagnosed as

having chronic silicosis. Parker concluded that there were a number of

inadequately protected individuals among above-ground workers.

All drillers and other miners must be protected from the inhalation

hazard of respirable drill dust. In the history of rock drilling,

various control techniques have been developed to reduce the amount of

dust emitted from the drill. Installing drill dust controls at the

source can reduce the amount of dust emitted and is effective in

protecting all miners at a mine. Many of these source-control

techniques are readily available and effective in the prevention of

pneumoconiosis.

B. Background

1. Metal and Nonmetal Mining

The Public Health Service has reported that drilling was one of the

most prolific dust-producing operations to which miners were exposed

(Silicosis in the Metal Mining Industry, 1963). In that study, 11

percent of the samples collected for drilling operations contained

excessive concentrations of silica-bearing dust. The study also cited

improper ventilation, dry collaring of holes, and defective equipment

as the primary causes of overexposure. In Medicine in the Mining

Industries (1972), wet drilling was recognized as an efficient means of

dust control.

Existing Secs. 56/57.5003 for metal and nonmetal mines require that

drill holes be collared and drilled wet or that other efficient dust

control measures be used when drilling non-water-soluble materials.

Efficient dust control measures also are required when drilling water-

soluble materials. MSHA issues a citation when a drill dust control is

missing, defective, or obviously ineffective by sight. In those cases

where it is not obvious that a control is ineffective, an MSHA

inspector has the option of reviewing the manufacturer's specifications

or other pertinent data, or sampling to determine its effectiveness.

Currently, MSHA issues about 90 citations and 3 orders per year for

violations of Secs. 56/57.5003.

2. Coal Mining

The development of silicosis and pneumoconiosis among underground

coal miners has been well documented, particularly among roof bolters

and transportation workers. Existing Secs. 70.400 through 70.400-3

address drill dust controls at underground coal mines. MSHA issues a

citation for a violation of Sec. 70.400 if visual observation indicates

that the drill dust controls on the equipment are not functioning

properly. Currently, MSHA issues about 15 such citations per year.

Section 72.630 of the final rule is comparable to existing Secs. 70.400

through 70.400-3 and MSHA's current interpretation of the regulation.

Likewise, Sec. 72.630 is a work practice standard that does not require

sampling.

Surface coal miners were not recognized as facing as serious a risk

as underground coal miners for many years (Parker et al., 1989).

Evidence has indicated that highwall drill operators and helpers at

surface coal mines have an increased risk of pneumoconiosis. Re-

analysis by Banks et al. (1983) of data from a previous U.S. Public

Health Service survey of surface coal miners, after exclusion of miners

with underground mining experience, showed that 38 percent of the cases

of pneumoconiosis in surface coal miners occurred in drill-crew members

even though this group comprised only 11 percent of the study

population.

In a 1984 evaluation of the prevalence of pneumoconiosis in surface

coal mine drillers, Amandus et al. found a significantly higher

incidence of category 1 or higher pneumoconiosis in persons with more

than 10 years surface drilling experience than in those with less than

10 years or no drilling experience. Results of this study also

indicated that the average coal mine dust level was significantly

higher among drillers than that found for all miners.

Later Piacitelli et al. (1990) reported that the respirable coal

mine dust samples submitted by coal mine operators and MSHA inspectors

from 1982 to 1986 were usually well below the 2.0 mg/m3 allowable

limit for all surface job categories. However, samples collected for

highwall drillers and helpers indicated that 78 percent and 77 percent,

respectively, exceeded the quartz exposure limit and that 10 to 15

percent of miners in both categories exceeded the 2.0 mg/m3

respirable coal mine dust standard.

Between 1989 and 1993, MSHA issued 112 citations for exceeding the

allowable limit for respirable dust on highwall drill operators and

helpers, of which 62 were for exceeding the 2.0 mg/m3 respirable

dust standard. The remaining 50 citations were issued for exceeding the

reduced respirable dust standard due to quartz content. As of July

1993, MSHA had placed 79 active highwall drills on a reduced respirable

dust standard due to the quartz concentration in respirable dust

samples collected on the drill operators. Also, there are 410 active

roof bolters in underground coal mines on a reduced respirable dust

standard due to quartz concentration on collected respirable dust

samples.

Notwithstanding Agency enforcement efforts, cases of silicosis

continue to be reported among surface coal miners. Therefore, in 1989,

MSHA proposed that drillers be protected at surface operations and that

the requirements be clarified for underground drillers. The final rule

is a work practice standard that does not require sampling. This

standard, in conjunction with existing regulations, is intended to

provide miners with more protection from exposures to harmful amounts

of silica and respirable coal mine dust.

C. Drill Dust--Toxicity

Pneumoconiosis began to receive increased attention toward the end

of the last century as a result of the introduction of machine drills

and the large quantities of dust they generate. Silicosis has long been

recognized as a health risk in rock drillers (Silicosis in the Metal

Mining Industry, 1963). In the past, rock drillers in underground coal

mines were known to have developed silicosis, but drillers at surface

coal mines were not considered to be at significant risk (Fairman et

al., 1977). However, more recent studies indicate that surface rock

drillers are being diagnosed with silicosis as well as other

pneumoconioses (Banks et al., 1983; Parker et al., 1989; Goodman et

al., 1992; Amandus et al., 1984; Piacitelli et al., 1990). A study

conducted by NIOSH in 1987 of silica dust exposure to drill crews

drilling overburden on a highwall at a surface coal mine indicated the

occurrence of significant overexposures and a prevalence of

pneumoconiosis five times greater than other surface workers (NIOSH

MHETA 87-173-1882).

The August 1992 CDC/NIOSH Alert on Rock Drillers referenced a

number of cases of silicosis among miners. One case involved an

individual who first experienced respiratory symptoms in 1986 at age 33

(Goodman et al., 1992). The subject was a quarry driller using wet

methods to suppress drill dust from 1973 to 1983. After 1983, he worked

primarily as a driller at a surface coal mine using no controls. The

miner died in 1991 of progressive respiratory failure.

Another driller reported respiratory problems in 1979 at age 34

(Banks et al., 1983). His history indicated that for the previous 5

years he had operated a rotary drill at a surface coal mine using dry

drilling methods. This miner died of respiratory failure in 1981. A

medical survey of nine other drillers working for the same company

found two additional miners, ages 28 and 31, with accelerated silicosis

after fewer than 6 years exposure.

One hospital in West Virginia reported seven cases of silicosis in

surface miners from 1978 to 1988. The cases involved miners with a

median age of 35 working in surface drilling for an average of 6 years

(Parker et al., 1989). One case had active tuberculosis. In addition, a

second possible case of tuberculosis was identified.

Ezenwa (1982) studied environmental and host factors in mines and

mills. In Quebec metal mines, Ezenwa found that a significantly larger

portion of miners who worked in drilling and crushing (associated with

high dust levels) developed silicosis in 15 years relative to other

occupations over the same time period. Of the 35 men with accelerated

silicosis, 37 percent had working experience as drillers.

D. Drill Dust Control--Technology

Various effective drill dust control techniques have been developed

that control the dust at the source. Many of these techniques are

readily available and effective in the prevention of respirable drill

dust overexposures. In addition, these dust control techniques can

reduce the hazard from drill dust for other miners in the mine as

opposed to personal respiratory protection equipment that only protects

the individual wearing it, and then only if worn properly.

Most failures of drill dust controls are readily identified and

easily corrected. Rather than mechanical breakdown of the controls,

malfunctions are generally the result of oversights or poor

maintenance, such as failure to turn on water, to fill water-holding

tanks, or to empty filters.

The general types of dust controls for rock drilling are wet

methods, dry methods, and ventilation control in underground coal

mines. Wet drilling methods are known to be effective for dust control

with non-water-soluble materials. These methods have been used as early

as 1922 and are inexpensive, practical, reliable, and effective in

controlling drill dust (Silicosis in the Metal Mining Industry, 1963).

Examples of wet drilling controls include the introduction of water

through a hollow drill stem, flooding of drill-holes, and water sprays.

Dry methods include various methods to capture the dust at the source

(the drill-hole), usually by vacuum, with subsequent removal of the

dust from the work area air by filtration or other means. Effective dry

dust collectors are readily available from several equipment

manufacturers for drilling both water-soluble and non-water-soluble

materials. General ventilation is not usually effective in underground

coal mines for drill dust control, unless it can rapidly disperse and

carry away the drill dust as well as direct the dust away from any

workers in the area.

E. Summary and Explanation of Rule

1. Sections 58/72.620

Section 58.620 is a recodification with no substantive change of

existing Secs. 56/57.5003, which addresses drill dust control at metal

and nonmetal mines. Section 72.620 established new requirements for

drill dust control at surface coal mines and surface areas of

underground coal mines. The final rule provides that drill holes be

collared and drilled wet or that other effective dust control measures

be used when drilling non-water-soluble material. The final rule also

requires effective dust control measures when drilling water-soluble

material.

NIOSH supported establishing rules for drill dust control at

surface coal mines because the potential exists for significant

overexposure to respirable free silica.

Many commenters objected to the specific control requirements

contained in proposed Secs. 58/72.620. These commenters recommended

that MSHA delete all of the existing and proposed drill dust control

standards and suggested that any new regulations addressing this issue

be performance oriented. Commenters stated that when judging how to

reduce miners' exposure to drill dust, operators should be given wide

discretion and be allowed to take into account differences in mine

conditions and mining operations.

Other commenters stated that MSHA should provide the same

compliance options to metal and nonmetal and surface coal mine

operators as are currently provided to underground coal mine operators.

These commenters recommended that the language of proposed Sec. 72.630

be made applicable to all mines. These commenters stated that by

requiring wet drilling, MSHA would be suppressing the development of

new technology and that the Agency was not taking into consideration

other effective measures of dust control, such as positive pressure

cabs.

The final rule allows mine operators the option of using controls

that are both practical and effective in controlling miners' exposures

to drill dust. The methods listed in the final rule are basic and

effective control technologies that are readily available to mine

operators. In addition, the phrase ``or other effective dust control

measures'' is included in the final rule to enable mine operators to

use methods other than those specifically listed in the standard.

MSHA's primary concern is that any drill dust control method relied

upon by the operator for the protection of miners' health have a level

of proven effectiveness. As a result, the proposed language in

Secs. 58/72.620 is retained in the final rule.

Likewise, it is MSHA's intent that the final rule allow new

technology. New methods of drill dust control may be used if their

effectiveness can be demonstrated. In the same manner, new types of

drilling may be developed and used if they include controls that are

effective in controlling drill dust. Metal and nonmetal and surface

coal mine operators do not have to seek MSHA approval before installing

``effective'' dust control technology.

MSHA agrees that positive pressure cabs are effective in

controlling exposures to dust for persons located within the cabs.

However, other miners may be working in the area. Because cabs do not

control drill dust at the source of generation, they are not adequate

to protect the health of miners located outside the cabs who are

exposed to the drill dust.

Many commenters also stated that the proposed standards would be

redundant and burdensome. They expressed concern that controls would be

required without regard to actual exposures which mine operators are

otherwise required to maintain within permissible exposure limits.

These commenters stated that the presumption that all drill operators

are overexposed unless there is a dust control system installed on the

drill is not valid. These commenters recommended that citations for

drill dust control be issued only when sampling data indicates that a

miner is overexposed.

MSHA disagrees with these commenters because the hazard associated

with drilling operations is so serious and the exposure so variable

that a permissible exposure limit alone cannot be relied upon as the

primary means of controlling drill dust exposure. The final rule

requires that effective drill dust controls be provided, regardless of

exposure. MSHA's experience has shown that drilling without effective

dust controls is highly likely to result in overexposure, not only to

the drill operator but also to other workers in the drilling area. Dust

generated by drills underground can be carried to other areas of the

mine by the ventilation system, creating contaminated air throughout

the mine and exposing unprotected miners. There is evidence that the

percentage of time that drill operators are overexposed is high enough

to warrant controls (Banks et al., 1983). In addition, due to the

nature of the drilling activity, the exposure concentration is not

always consistent and, in some instances, a miner can be acutely

exposed before sampling data indicates an overexposure.

One commenter recommended deleting the second sentence of Secs. 58/

72.620, ``or other effective dust control measures,'' and stated that

collaring and wet drilling should be the preferred means of drill dust

control. This commenter stated that a standard requiring only collaring

and wet drilling would be easier for MSHA to enforce because the

provision for ``alternative methods'' would require the Agency to

assess data. This commenter also suggested that operators could file a

petition for modification with MSHA if they wanted to use an

alternative dust control method.

MSHA recognizes that wet drilling is an established practice at

metal and nonmetal mines. However, there are other methods of drill

dust control, such as dry dust collectors, which are also effective in

controlling drill dust. A requirement permitting only wet drilling and

dry dust collection could stifle new technology that could be effective

in the control of drill dust. MSHA has had experience enforcing this

standard at metal and nonmetal mines and will enforce the requirements

similarly at surface operations of coal mines. In addition, the Mine

Act does not allow mine operators to petition for modification of

health standards.

Some commenters expressed concern that the proposed standards on

drill dust control would give too much discretion to MSHA inspectors.

One commenter stated that an inspector could arrive at a mine, observe

some dust coming from a drill, and issue a citation based solely on his

subjective conclusion that the dust control method being used was ``not

effective.'' Some commenters recommended that an inspector be allowed

to issue a citation only when an operator fails to have drill dust

controls in place or when sampling results indicate an overexposure.

Under the final rule, MSHA will cite a mine operator when a dust

control is missing, defective, or obviously ineffective by visual

inspection. In those cases where it is not obvious that a control is

effective, MSHA inspectors would have the option of reviewing

manufacturer's specifications or other pertinent data relative to the

design and operation of the dust control or, if practical, collecting

samples to evaluate its effectiveness.

One commenter stated that MSHA needed to consider that climatic

conditions play an important role in ``effective'' dust control. This

commenter used wet and dry dust-collection systems and, under certain

conditions, each method could be rendered inoperable. This commenter

stated that the wet systems fail in cold temperatures, and the dry

vacuum systems tend to plug when the drill bit enters moist areas. This

commenter recommended that, as a temporary solution, operators be

allowed to issue respiratory protection to the affected miners when

controls fail due to temporary weather conditions.

MSHA agrees that problems can be encountered by drillers when using

wet or dry drilling methods. However, there are precautions that the

operator can take to reduce these problems, such as adding antifreeze

to the water. Because of the need to control drill dust at the source,

effective drill dust controls would not include personal protective

equipment or administrative controls. After reviewing the comments

received, MSHA has retained the proposed language in the final rule.

2. Section 72.630

Section 72.630, which addresses drill dust control at underground

coal mines, recodifies existing Secs. 70.400 through 70.400-3 and

strengthens the maintenance requirement for dust collectors.

Paragraph (a) recodifies existing Sec. 70.400 and requires that

dust resulting from drilling in rock be controlled by use of

permissible dust collectors, or by water, or water with a wetting

agent, or by ventilation, or by any other method or device approved by

the Secretary in the ventilation plan that is as effective in

controlling the dust. This requirement is not intended to limit the

introduction of new technology into the mining environment. However,

because of health and safety concerns at underground coal mines, MSHA

believes that the Agency should evaluate the effectiveness of new

technology before it is used.

Some commenters objected to the specific control requirements

contained in the standard. Many recommended that MSHA delete all of the

existing and proposed drill dust control standards and suggested that

any new regulations addressing this issue be performance oriented. Some

stated that, when judging how to reduce miners' exposure to drill dust,

operators should be given wide discretion to take into account

differences in mine conditions and mining operations.

A specific standard addressing the health hazards associated with

drill dust continues to be necessary due to the likelihood of

overexposure inherent in such operations. Underground coal mine

operators have the option of using controls which are both practical

and effective in controlling miners' exposure to drill dust. The

methods listed in the final rule are basic and effective control

technologies that are readily available to underground coal mine

operators. In addition, the phrase ``or by any other method or device

approved by the Secretary that is as effective in controlling the

dust'' is included in the final rule in order to enable mine operators

to use methods other than those specifically listed in the standard. As

a result, the final rule makes only nonsubstantive editorial changes to

Secs. 70.400 through 70.400-3 and recodifies them as Sec. 72.630.

As with Sec. 72.620, many commenters stated that the proposed

standard would be redundant and burdensome because controls would be

required with no consideration of actual exposures. These commenters

stated that the presumption that all drill operators are overexposed

unless there is a dust control system installed on the drill is not

valid. These commenters recommended that citations for drill dust

control be issued only when sampling data indicates that a miner is

overexposed. As stated above, because the hazard associated with

drilling operations is so serious and exposure so variable, a

permissible exposure limit alone cannot be relied upon as the primary

means of controlling drill dust exposure.

As stated previously, MSHA will continue to cite a mine operator

when a dust control is missing, defective, or obviously visually

ineffective. In those cases where it is not obvious that a control is

effective, MSHA inspectors will continue to have the option of

reviewing manufacturer's specifications or other pertinent data

relative to the design and operation of the dust control, or of

sampling to determine its effectiveness.

Paragraph (b) recodifies existing Sec. 70.400-1 which requires

control of drill dust through the use of permissible dust collectors.

In addition, as proposed, a new provision clarifies that dust

collectors must be maintained in permissible and operating condition

when they are provided as a method of controlling dust. The majority of

commenters supported MSHA in requiring that dust collectors be

maintained in permissible and operating condition. NIOSH commented that

they supported MSHA's proposed rule for drill dust control at

underground coal mines and that the proposed addition of maintenance

requirements for dust collectors was appropriate for limiting the

exposure of miners in these operations to respirable free silica.

Paragraph (c) recodifies Sec. 70.400-2 with no change in the

existing requirement that water used to control drill dust be applied

through a hollow drill steel or stem or by the flooding of vertical

drill holes in the floor. Some commenters recommended that paragraph

(c) be deleted because they stated that the provision would place

limits on the options available to mine operators for the control of

drill dust at underground coal mines. One commenter stated that the

wording in the proposed rule would place unnecessary limits on the

methods by which water could be used to control dust. Another commenter

stated that the wording in the proposed rule would limit the use of new

technology and that the requirement to wet drill would be infeasible

and difficult to implement in areas of low water availability and high

altitude.

MSHA does not intend for this standard to be technology stifling.

As indicated earlier, the operator is not restricted to the methods

listed in the standard and, if circumstances are such that wet drilling

is not practical or feasible, the operator has the option of using

other effective methods approved by the Secretary of Labor. Wet

drilling can be an inexpensive, practical, and effective means of

controlling miners' exposure to drill dust at underground coal mines.

This practice is currently in use at underground coal mines for

drilling non-water-soluble materials.

Paragraph (d) recodifies existing Sec. 70.400-3 with no change in

the existing requirement that air currents be so directed that the dust

is readily dispersed and carried away from the drill operator or other

workers in the area. Many commenters stated that this provision was

unnecessary because a mine operator would be instructed by MSHA not to

direct the ventilation current toward a drill operator. Other

commenters stated that the provision that permits the use of

``ventilation * * * that is effective in controlling the dust'' implies

that MSHA will have to determine noncompliance through the

demonstration of an overexposure to a permissible exposure limit. One

commenter recommended deleting paragraph (d), stating that the

preferred means of drill dust control should be limited to permissible

dust collectors, water, or water with a wetting agent. This commenter

stated that ventilation is less effective in the control of drill dust

and harder for MSHA to enforce.

MSHA recognizes that ventilation may not always be a practical

method of drill dust control and that it is not the predominant method

used in underground coal mines. Under some circumstances, continuous

mining machines and roof bolters work on a single split of air, and

this can result in only the drillers being protected while persons

working downwind could be exposed. If proper precautions are taken,

however, ventilation can be an effective method of drill dust control.

MSHA, therefore, has not deleted paragraph (d). MSHA will continue to

determine compliance with this requirement under the final rule as it

has enforced Sec. 70.400-3; i.e., through the measurement of air

quantity or other measures set forth in a mine's ventilation and

methane and dust control plan. MSHA does not intend that exposure

samples be the routine method of determining compliance with this

paragraph.

V. References

Amandus, H.E. et al., ``A Re-evaluation of Radiological Evidence

from a Study of U.S. Strip Coal Miners,'' Arch Environ Health

39(5):346-351, September/October 1984.

Bailey, W.C. et al., ``Silico-Mycobacterial Disease in

Sandblasters,'' Am Rev Respir Dis 110:115-125, 1974.

Banks, D.E. et al., ``Silicosis in surface coalmine drillers,''

Thorax 38:275-278, 1983.

Berkow, R., ed., The Merck Manual of Diagnosis and Therapy (15th

Edition), 1987. pp. 679-681.

Buechner, H.A. and A. Ansari, ``Acute Silico-Proteinosis,'' Dis

Chest 55(4):274-284, April 1969.

CDC (Centers for Disease Control), ``Silicosis: Cluster in

Sandblasters--Texas, and Occupational Surveillance for Silicosis,''

MMWR 39(25):433-437, June 1990.

CDC/NIOSH, ``Alert--Preventing Lead Poisoning in Construction

Workers (Rev. Ed.),'' DHHS (NIOSH) Pub. No. 91-116a, April 1992.

CDC/NIOSH, ``Alert--Preventing Silicosis and Deaths From

Sandblasting,'' DHHS (NIOSH) Pub. No. 92-102, August 1992.

CDC/NIOSH, ``Alert--Preventing Silicosis and Deaths in Rock

Drillers,'' DHHS (NIOSH) Pub. No. 92-107, August 1992.

Claypool, W.D., ``Pulmonary Alveolar Proteinosis,'' Ch. 57 in

Pulmonary Diseases and Disorders (2nd Edition), Vol. 2, by A.P.

Fishman, 1988. pp. 893-900.

Craighead, J.E. et al., ``Diseases Associated with Exposure to

Silica and Nonfibrous Silicate Minerals,'' Arch Pathol Lab Med

112:673-720, July 1988.

Ezenwa, A.O., ``Studies of Environmental and Host Factors

Influencing Personal Differences in Response to Industrial Silica

Dust Exposure,'' Ann Occup Hyg 26(1-4):745-752, 1982.

Fairman, R.P. et al., ``Respiratory Status of Surface Coal Miners in

the United States,'' Arch Environ Health 32(1):211-215, September/

October 1977.

Goodman, G.B. et al., ``Acute Silicosis Responding to Corticosteroid

Therapy,'' Chest 101:366-370, 1992.

Heppleston, A.G. et al., ``Experimental Alveolar Lipo-Proteinosis

Following the Inhalation of Silica,'' J Path 101(4):293-307, 1970.

MacKay, G.R. et al., ``Fibrogenic potential of slags used as

substitutes for sand in abrasive blasting operations,'' AIHAJ

41:836-842, November 1980.

Merchant, J.A., ed., Occupational Respiratory Diseases, DHHS (NIOSH)

Pub. No. 86-102, September 1986, pp. 219-241.

Merewether, E.R.A., ``The Risk of Silicosis in Sand-Blasters,''

Tubercle 17(25):385-391, June 1936.

Mickelsen, R.L. and P.A. Froehlich, ``Lead-Based Paint Removal Using

Recyclable Steel Abrasive (Abstract),'' Paper presented at American

Industrial Hygiene Conference & Exposition '93, New Orleans, LA, May

15-21, 1993, p. 9.

Morrow, P.E., ``Possible Mechanisms to Explain Dust Overloading of

the Lungs,'' Fundamental and Applied Toxicology 10:369-384, 1988.

NIOSH, ``Health Hazard Evaluation Report,'' (MHETA 87-173-1882) at

Jeddo Highland Coal Co., West Pittston, PA, August 1987.

NIOSH, ``Occupational Exposure to Crystalline Silica,'' HEW (NIOSH)

Pub. No. 75-120, 1974.

Owens, M.W. et al., ``Case Report: Sandblaster's Lung with

Mycobacterial Infection,'' Am J Med Sci 295(6):554-557, June 1988.

Parker, J.E. et al., ``Surface Coal Mine Drillers and Silicosis: The

Ten Year West Virginia Experience (Abstract),'' Am Rev Respir Dis

139:A490, 1989.

Piacitelli, G.M. et al., ``Respirable Dust Exposures in U.S. Surface

Coal Mines (1982-1986),'' Arch Environ Health 45(4):202-209, July/

August 1990.

Public Health Service and Bureau of Mines, ``Silicosis in the Metal

Mining Industry,'' Public Health Service Pub. No. 1076, 1963.

Rekus, J.F., ``Working on Structural Steel: The Lead Hazard,''

Journal of Protective Coatings & Linings 5(10):38-44, 1988.

Rogan, J.M., ed., Medicine in the Mining Industries, 1972.

Rubin, E. et al., ``Pulmonary Alveolar Proteinosis,'' Radiology

135:35-41, April 1980.

Samimi, B. et al., ``Respirable Silica Dust Exposure of Sandblasters

and Associated Workers in Steel Fabrication Yards,'' Arch Environ

Health 29:61-66, August 1974.

Stettler, L.E. et al., ``Fibrogenicity and Carcinogenic Potential of

Smelter Slags Used as Abrasive Blasting Substitutes,'' J Toxicol and

Environ Health 25:35-56, 1988.

Suratt, P.M. et al., ``Case Reports: Acute Silicosis in Tombstone

Sandblasters,'' Am Rev Respir Dis 115:521-529, 1977.

Vallyathan, V. et al., ``Generation of Free Radicals from Freshly

Fractured Silica Dust,'' Am Rev Respir Dis 138:1213-1219, 1988.

Ziskind, M. et al., ``State of the Art: Silicosis,'' Am Rev Respir

Dis 113:643-665, 1976.

VI. Executive Order 12866 and the Regulatory Flexibility Act

In accordance with Executive Order 12866, MSHA prepared a final

regulatory impact analysis (RIA) to determine the incremental costs and

benefits associated with the final rule on drill dust control and

abrasive blasting. MSHA has determined in its RIA that this rule would

neither result in major cost increases nor have an effect of $100

million or more on the economy. The RIA, which is available from MSHA

upon request, is summarized as follows.

Benefits

The final rule enhances safety and health, and none of these

revisions reduce miner protection. In providing an estimate of the

potential benefits that is based on previous coal miner cases, it needs

to be noted that some of these miners may have received a majority of

their exposures in mining activities other than highwall drilling. In

addition, metal and nonmetal mines, which have had to comply with these

drill dust controls, perform considerably more highwall drilling than

do coal mines. Whereas 30 surface coal miner pneumoconiosis cases were

reported to MSHA during the previous 10 years, only 5 metal and

nonmetal pneumoconiosis cases were reported to MSHA during this period.

As a result, MSHA determined that compliance with the new requirements

for drill dust controls at surface coal mines would have prevented

between 10 and 20 of the 30 surface coal miner pneumoconiosis cases

reported to MSHA during the preceding 10 years, for an average of 1 to

2 cases prevented annually.

Even though MSHA was unable to identify any specific case that

would have been prevented by the new abrasive blasting requirements,

compliance with the final rule will help to prevent potential future

cases of silicosis and other dust diseases of the lungs.

Costs

MSHA has compared the costs associated with the existing

requirements with the costs of the new requirements. Noting that

approximately 250 coal highwall drillers will require some retrofitting

at unit costs of about $2,500 for adding a collector or baghouse, about

$8,000 for installing a dry dust collecting system, and about $7,000

for installing a wet drilling system, MSHA calculated that compliance

with the final rule for drill dust controls will cost the coal mining

industry about $950,000 in first-year costs, which would translate into

about $155,000 in annualized costs. Annual costs for such items as

maintenance of dust-collection systems, filter replacement, etc., are

estimated to be about $95,000. Thus, the total annualized plus annual

compliance cost is projected to be about $250,000.

With respect to the abrasive blasting requirements, MSHA determined

that about 55 metal and nonmetal mines and 20 coal mines would be

required to purchase new respiratory protective equipment. The unit

costs for this equipment can range from $900 for a powered, air-

purifying respirator (PAPR); $1,450 for an air-supplied hood

retrofitted with an existing air compressor; $2,200 for an air-supplied

hood retrofitted with an air distribution system; and between $1,000

and $1,500 for an abrasive blasting cabinet.

MSHA calculated that compliance with the final rule for abrasive

blasting will cost the metal and nonmetal mining industry about

$103,000 in first-year costs, which would translate into about $17,000

in annualized costs. Annual costs for such items as maintenance, filter

replacement, etc., are estimated to be about $10,000. Thus, the total

metal and nonmetal annualized plus annual compliance cost is projected

to be about $27,000.

For coal mining, MSHA calculated that compliance with the final

rule for abrasive blasting will cost about $40,000 in first-year costs,

which would translate into about $7,000 in annualized costs. Annual

costs for such items as maintenance, filter replacement, etc., will be

about $4,000. Thus, the total coal annualized plus annual compliance

cost will be about $11,000.

MSHA's final rule will have a minimal impact upon labor

productivity, profits, prices, mining output, and mining employment.

The Agency foresees no detrimental economic impact to this industry.

Regulatory Flexibility Act

The Regulatory Flexibility Act requires that agencies evaluate and

include, wherever possible, compliance alternatives that minimize any

adverse impact on small businesses when developing regulatory

standards. This final rule includes alternative compliance methods,

several of which will directly affect small mining operations.

MSHA determined that small mines will incur first-year costs of

about $248,000, or annualized costs of about $41,000. Annual costs for

small mines will be about $25,000. At the same time, MSHA determined

that large mines will incur first-year costs of about $846,000, or

annualized costs of about $138,000. Annual costs for large mines will

be about $84,000.

MSHA determined that these new provisions will not generate a

substantial cost increase for small mines. The lack of a substantial

cost increase for small mines in conjunction with the fact that similar

hazards exist in both large and small mining operations indicates that

regulatory relief is not warranted for small mining operations.

Therefore, MSHA has determined that the final rule will not have a

significantly adverse impact upon a substantial number of small

entities.

VII. Paperwork Reduction Act

This final rule contains no information paperwork requirements

subject to the Paperwork Reduction Act of 1980.

Derivation Table

The following derivation table lists the final rule with the

existing standard numbers from which it is derived.

------------------------------------------------------------------------

New section Old section

------------------------------------------------------------------------

58.610(a)....................................... 56 and 57.5010.

58.610(b)....................................... 57.5016.

58.620.......................................... 56 and 57.5003.

72.610.......................................... New.

72.620.......................................... New.

72.630(a)....................................... 70.400.

72.630(b)....................................... 70.400-1.

72.630(c)....................................... 70.400-2.

72.630(d)....................................... 70.400-3

------------------------------------------------------------------------

Redesignation Table

The following redesignation table lists the existing standard with

the final rule standard numbers.

------------------------------------------------------------------------

Old section New section

------------------------------------------------------------------------

56 and 57.5003........................................ 58.620

56 and 57.5010........................................ 58.610(a)

57.5016............................................... 58.610(b)

70.400................................................ 72.630(a)

70.400-1.............................................. 72.630(b)

70.400-2.............................................. 72.630(c)

70.400-3.............................................. 72.630(d)

------------------------------------------------------------------------

List of Subjects in 30 CFR Parts 56, 57, 58, 70, and 72

Mine safety and health, Surface mining, Underground mining.

Dated: February 11, 1994.

J. Davitt McAteer,

Assistant Secretary for Mine Safety and Health.

Accordingly, chapter I of title 30 of the Code of Federal

Regulations is amended as set forth below:

PART 56--[AMENDED]

1. The authority citation for part 56 continues to read as follows:

Authority: 30 U.S.C. 811, 957, and 961.

Sec. 56.5003 [Removed]

2. Section 56.5003 is removed.

Sec. 56.5010 [Removed]

3. Section 56.5010 is removed.

PART 57--[AMENDED]

4. The authority citation for part 57 continues to read as follows:

Authority: 30 U.S.C. 811, 957, and 961.

Sec. 57.5003 [Removed]

5. Section 57.5003 is removed.

Sec. 57.5010 [Removed]

6. Section 57.5010 is removed.

Sec. 57.5016 [Removed]

7. Section 57.5016 is removed.

8. A new part 58 is added to subchapter N, 30 CFR chapter I to read

as follows:

PART 58--HEALTH STANDARDS FOR METAL AND NONMETAL MINES

Subpart A--General

Sec.

58.1 Scope.

Subparts B Through D--[Reserved]

Subpart E--Miscellaneous

58.610 Abrasive blasting.

58.620 Drill dust control.

Authority: 30 U.S.C. 811, 957, and 961.

Subpart A--General

Sec. 58.1 Scope.

The health standards in this part apply to all metal and nonmetal

mines.

Subpart E--Miscellaneous

Sec. 58.610 Abrasive blasting.

(a) Surface and underground mines. When an abrasive blasting

operation is performed, all exposed miners shall use in accordance with

Secs. 56/57.5005 respirators approved for abrasive blasting by NIOSH or

the operation shall be performed in a totally enclosed device with the

miner outside the device.

(b) Underground areas of underground mines. Silica sand or other

materials containing more than 1 percent free silica shall not be used

as an abrasive substance in abrasive blasting.

Sec. 58.620 Drill dust control.

Holes shall be collared and drilled wet, or other effective dust

control measures shall be used, when drilling non-water-soluble

material. Effective dust control measures shall be used when drilling

water-soluble materials.

PART 70--[AMENDED]

9. The authority citation for part 70 is revised to read as

follows:

Authority: 30 U.S.C. 811, 813(h), 957, and 961.

Secs. 70.400, 70.400-1, 70.400-2 and 70.400-3 [Removed].

10. Sections 70.400, 70.400-1, 70.400-2, and 70.400-3 are removed.

11. A new part 72 is added to subchapter O to read as follows:

PART 72--HEALTH STANDARDS FOR COAL MINES

Subpart A--General

Sec.

72.1 Scope.

Subparts B Through D--[Reserved]

Subpart E--Miscellaneous

72.610 Abrasive blasting.

72.620 Drill dust control at surface mines and surface areas of

underground mines.

72.630 Drill dust control at underground areas of underground

mines.

Authority: 30 U.S.C. 811, 813(h), 957, and 961.

Subpart A--General

Sec. 72.1 Scope.

The health standards in this part apply to all coal mines.

Subpart E--Miscellaneous

Sec. 72.610 Abrasive blasting.

(a) Surface and underground mines. When an abrasive blasting

operation is performed, all exposed miners shall properly use

respirators approved for abrasive blasting by NIOSH, or the operation

shall be performed in a totally enclosed device with the miner outside

the device.

(b) Underground areas of underground mines. Silica sand or other

materials containing more than 1 percent free silica shall not be used

as an abrasive substance in abrasive blasting.

Sec. 72.620 Drill dust control at surface mines and surface areas of

underground mines.

Holes shall be collared and drilled wet, or other effective dust

control measures shall be used, when drilling non-water-soluble

material. Effective dust control measures shall be used when drilling

water-soluble material.

Sec. 72.630 Drill dust control at underground areas of underground

mines.

(a) Dust resulting from drilling in rock shall be controlled by use

of permissible dust collectors, or by water, or water with a wetting

agent, or by ventilation, or by any other method or device approved by

the Secretary that is as effective in controlling the dust.

(b) Dust collectors. Dust collectors shall be maintained in

permissible and operating condition. Dust collectors approved under

Part 33--Dust Collectors for Use in Connection with Rock Drilling in

Coal Mines of this title or under Bureau of Mines Schedule 25B are

permissible dust collectors for the purpose of this section.

(c) Water control. Water used to control dust from drilling rock

shall be applied through a hollow drill steel or stem or by the

flooding of vertical drill holes in the floor.

(d) Ventilation control. To adequately control dust from drilling

rock, the air current shall be so directed that the dust is readily

dispersed and carried away from the drill operator or any other miners

in the area.

[FR Doc. 94-3591 Filed 2-17-94; 8:45 am]

BILLING CODE 4510-43-P