Update on the Status of the Superfund Substance-Specific Applied Research Program

SUMMARY: This Notice provides the status of ATSDR's Superfund-mandated

Substance-Specific Applied Research Program (SSARP), which was last

updated in a Federal Register notice in 1996 (61 FR 14420). Authorized

by the Comprehensive Environmental Response, Compensation, and

Liability Act of 1980 (CERCLA, also known as the Superfund statute), as

amended by the Superfund Amendments and Reauthorization Act of 1986

(SARA) (42 U.S.C. 9604(i)), this research program was initiated on

October 17, 1991. At that time, a list of priority data needs for 38

priority hazardous substances frequently found at waste sites was

announced in the Federal Register (56 FR 52178). The list was

subsequently revised based on public comments and published in final

form on November 16, 1992 (57 FR 54150).

The 38 substances, each of which is found on ATSDR's Priority List

of Hazardous Substances (62 FR 61332, November 17, 1997), are aldrin/

dieldrin, arsenic, benzene, beryllium, cadmium, carbon tetrachloride,

chloroethane, chloroform, chromium, cyanide, p,p'-DDT,DDE,DDD, di(2-

ethylhexyl) phthalate, lead, mercury, methylene chloride, nickel,

polychlorinated biphenyl compounds (PCBs), polycyclic aromatic

hydrocarbons (PAHs--includes 15 substances), selenium,

tetrachloroethylene, toluene, trichloroethylene, vinyl chloride, and

zinc.

On July 30, 1997, priority data needs for 12 additional hazardous

substances frequently found at waste sites were determined and

announced in the Federal Register (62 FR 40820). The 12 substances,

each of which is included in ATSDR's Priority List of Hazardous

Substances, are chlordane, 1,2-dibromo-3-chloropropane, di-n-butyl

phthalate, disulfoton, endrin (includes endrin aldehyde), endosulfan

(alpha-, beta-, and endosulfan sulfate), heptachlor (includes

heptachlor epoxide), hexachlorobutadiene, hexachlorocyclohexane (alpha-

, beta-, delta- and gamma-), manganese, methoxychlor, and toxaphene.

To date, 124 priority data needs have been identified for the first

set of 38 hazardous substances, and 64 priority data needs have been

identified for the second set of 12 hazardous substances. ATSDR fills

these data needs through regulatory mechanisms (test rules), private-

sector voluntarism, and the direct use of CERCLA funds. Additional data

needs are being addressed through an interagency agreement with the

National Toxicology Program (NTP), by ATSDR's Great Lakes Human Health

Effects Research Program, and other agency programs. To date, 79

priority data needs associated with the first set of 38 priority

substances (Table 1), and 23 priority data needs associated with the

second set of 12 priority substances (Table 2) are being addressed via

these mechanisms.

Table 1 also shows the progress ATSDR has made in filling research

needs for the first set of 38 hazardous substances. On the basis of

criteria developed by ATSDR, 14 priority data needs and 2 data needs

have been filled, 26 priority data needs have been reclassified as data

needs, and 2 additional priority data needs and 1 data need are

considered conditionally filled pending ATSDR peer review of the final

reports.

This Notice also serves as a continuous call for voluntary research

proposals. Private-sector organizations may volunteer to conduct

research to address specific priority data needs identified in this

Notice by indicating their interest through submission of a letter of

intent to ATSDR (see ADDRESSES section of this Notice). A Tri-Agency

Superfund Applied Research Committee (TASARC) composed of scientists

from ATSDR, NTP, and the Environmental Protection Agency (EPA), will

review all proposed voluntary research efforts.

DATES: ATSDR provides updates on the status of its Substance-Specific

Applied Research Program approximately every 3 years. ATSDR considers

the voluntary research effort to be important to the continuing

implementation of the SSARP. Therefore, the agency strongly encourages

private-sector organizations to volunteer at any time to conduct

research to fill data needs until ATSDR announces that other research

mechanisms are in place to address those specific data needs.

ADDRESSES: Private-sector organizations interested in volunteering to

conduct research may write to Dr. William Cibulas, Chief, Research

Implementation Branch, Division of Toxicology, ATSDR, 1600 Clifton

Road, NE., Mailstop E-29, Atlanta, Georgia 30333. Information about

pertinent ongoing or completed research that may fill priority data

needs cited in this Notice should be similarly addressed.

FOR FURTHER INFORMATION CONTACT: Dr. William Cibulas, Chief, Research

Implementation Branch, Division of Toxicology, ATSDR, 1600 Clifton

Road, NE., Mailstop E-29, Atlanta, Georgia 30333, telephone 404-639-

6306.

SUPPLEMENTARY INFORMATION:

Background

CERCLA as amended by SARA (42 U.S.C. 9604(i)) requires that ATSDR

(1) jointly with the EPA, develop and prioritize a list of hazardous

substances found at National Priorities List (NPL) sites, (2) prepare

toxicological profiles for these substances, and (3) assure the

initiation of a research program to address identified data needs

associated with the substances. Before starting such a program, ATSDR

will consider recommendations of the Interagency Testing Committee on

the type of research that should be done. This committee was

established under Section 4(e) of the Toxic Substances Control Act of

1976 (TSCA).

The major goals of the ATSDR SSARP are (1) to address the

substance-specific information needs of the public and scientific

community, and (2) to supply information necessary to improve the

database to conduct comprehensive public health assessments of

populations living near hazardous waste sites. We anticipate that the

information will enable the agency to establish linkages between levels

of contaminants in the environment and levels in human tissue and

organs associated with adverse health effects. Once such links have

been established, strategies to mitigate potentially harmful exposures

can be developed. This program will also provide data that can be

generalized to other substances or areas of science, including risk

assessment of chemicals, thus creating a scientific information base

for addressing a broader range of data needs.

On October 17, 1991, ATSDR announced the identification of the

priority data needs for 38 priority hazardous substances (56 FR 52178),

requested public comments, and invited private-sector organizations to

volunteer to conduct research to address specific priority data needs.

On November 16, 1992, the agency published a revised list of 117

priority data needs for these hazardous substances (57 FR 54150). Since

1992, the total number of priority

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data needs for the 38 substances has increased from 117 to 124 because

the database was reevaluated (Table 1). The 7 additional priority data

needs consist of 5 substances now considered as candidates for

subregistries of exposed persons (determined by the ATSDR Division of

Health Studies; the priority data needs for nickel, PCBs, toluene, and

zinc were added in 1996, and that for beryllium was added in 1998), and

2 new priority data needs for trichloroethylene.

Regarding the 2 additional priority data needs for

trichloroethylene, the need for intermediate-duration oral exposure

data resulted from the withdrawal of the corresponding minimal risk

level (MRL, a health guidance value) from the 1997 ATSDR updated

Toxicological Profile for Trichloroethylene (Table 1). The other new

priority data need for trichloroethylene is for a 1-species

developmental toxicity study with emphasis on developmental

neurotoxicity. Recent reports in humans, together with findings in

animals, suggest that developmental effects may be the most sensitive

end point for trichloroethylene.

Therefore, the proposed study may provide more definitive

information on dose-response relationships for these effects and more

fully characterize the potential for adverse health outcome in the

developing fetus.

Two additional changes from the 1992 list of priority data needs

have been made for tetrachloroethylene. The priority data need for

chronic-duration oral exposure data has been replaced by the need for

intermediate-duration oral exposure data because of the withdrawal of

the intermediate-duration oral MRL from the 1997 ATSDR updated

Toxicological Profile for Tetrachloroethylene (Table 1). ATSDR

considers it is more appropriate to obtain intermediate-duration data

before assigning priority to the conduct of chronic-duration studies.

With regard to the priority to obtain developmental toxicity data, the

use of 1-species (instead of the previously recommended 2-species) in

the study is now considered adequate based on reevaluation of the

database.

Table 1 also includes 3 PCB research needs that are not considered

``priority'' but were filled via voluntary research (see PDN ID#s 7G,

7H, and 7I).

On July 30, 1997, 77 priority data needs for 12 additional priority

hazardous substances were determined and announced in the Federal

Register (62 FR 40820). At that time, the 77 priority data needs

included the need to evaluate existing data on concentrations of all 12

substances in environmental media at hazardous waste sites. The agency

continues to recognize the need to collect, evaluate, and interpret

such data, but no longer considers these ``priority.'' This is because

a substantial amount of this information has already been collected

through individual state programs and the EPA's CERCLA activities.

Further, an ongoing effort at the agency is to evaluate the extant

information from these programs to better characterize the need for

additional site-specific information. Finally, during a recent

reevaluation of potential candidates for subregistries of exposed

persons conducted by ATSDR, manganese was removed from the candidate

pool; consequently, this priority data need was reclassified as a data

need. Therefore, the current total number of priority data needs

associated with the second set of 12 priority substances is now 64

(Table 2).

CERCLA section 104(i)(5)(D) states that it is the sense of Congress

that the costs for conducting this research program be borne by the

manufacturers and processors of the hazardous substances under TSCA and

by registrants under the Federal Insecticide, Fungicide, and

Rodenticide Act of 1972 (FIFRA), or by cost recovery from responsible

parties under CERCLA. To execute this statutory intent, ATSDR developed

a plan whereby parts of the SSARP are being conducted via regulatory

mechanisms (TSCA/FIFRA), private-sector voluntarism, and the direct use

of CERCLA funds.

The TASARC, composed of scientists from ATSDR, NTP, and EPA has

been set up to:

(1) Advise ATSDR on the assignment of priorities for mechanisms to

address data needs;

(2) Coordinate knowledge of research activities to avoid

duplication of research in other programs and under other authorities;

(3) Advise ATSDR on issues of science related to substance-specific

data needs; and

(4) Maintain a scheduled forum that provides an overall review of

the ATSDR SSARP.

TASARC has met eight times since the initiation of the SSARP. It

has guided referral of data needs to EPA and the associated development

of test rules through TSCA. In addition, it has endorsed the proposals

of several private-sector organizations to conduct voluntary research.

Furthermore, TASARC has become a forum for other federal agencies to

bring forth their research agenda. For example, it has coordinated

research efforts on hazardous pollutants with the Office of Air and

Radiation, EPA. TASARC has developed testing guidelines for

immunotoxicity; and it has endorsed the use of decision support

methodologies such as physiologically based pharmacokinetic (PBPK)

modeling and benchmark-dose modeling, where appropriate.

Additional data needs are being addressed through an interagency

agreement with NTP, by ATSDR's Great Lakes Human Health Effects

Research Program, and other agency programs. To date, 79 priority data

needs associated with the first set of 38 priority substances (Table

1), and 23 priority data needs associated with the second set of 12

priority substances (Table 2) are being addressed via these mechanisms.

Criteria for Evaluating Status of Priority Data Needs

To update the activities covered under the SSARP, criteria for

evaluating the status of the priority data needs were developed. Based

on these criteria and the review of the current literature, a priority

data need may be filled, reclassified as a data need, or unchanged.

Further, during the literature review, new studies may be identified

suggesting other effects of concern, such as those related to endocrine

disruptors and children's health, which have not been included in the

original list of priority data needs. In such cases, additional data

needs or priority data needs may be added to the research agenda.

The criteria for evaluating the status of the priority data needs

are described below.

General Criteria

1. A priority data need is filled:

If a study, specifically designed to address a priority

data need and conducted via any of the ATSDR implementation mechanisms,

has been completed and published in a peer-reviewed journal, or has

been accepted by ATSDR based on the recommendations of the agency's

peer reviewers, or

If an updated ATSDR toxicological profile or other recent

review document contains relevant new (peer reviewed and publicly

available) studies since the finalization of the priority data needs

document; and it is generally agreed that a priority data need no

longer exists.

Note: Priority data needs documents that describe ATSDR's

rationale for prioritizing research needs for each substance in

Tables 1 and 2 are available. See ADDRESSES section of this Notice.

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2. A priority data need is reclassified as a data need:

If an updated ATSDR toxicological profile or other recent

review document contains relevant new (peer reviewed and publicly

available) studies since the finalization of the priority data needs

document; however, in the data needs section of the toxicological

profile, a need for additional data to fully characterize the end point

is still identified, or

If a study addressing a priority data need has been

reviewed by members of the Tri-Agency Superfund Applied Research

Committee and it is agreed that a data need still exists although it is

no longer a priority (See priority data need ``Evaluation of the

environmental fate of cyanide in soil'' in Table 1), or

For any substance whose overall rank on the ATSDR Priority

List of Hazardous Substances falls below 275.

3. A priority data need is unchanged:

If no mechanism or information has been identified to

address the priority data need, or

If the ATSDR toxicological profile has not been updated

since the finalization of the priority data needs document (Exception:

See Section ``Specific Criteria'' for the priority data need ``Exposure

levels in humans''), or

If the priority data need is included in the ATSDR test

rule under development, or

If ongoing discussions between ATSDR and a private-sector

organization indicate that the priority data need is a candidate to be

addressed via the voluntary research program, or

If a study, specifically designed to address a priority

data need and conducted via any of the ATSDR implementation mechanisms,

is ongoing.

Specific Criteria

1. Priority data need, ``Inhalation and/or oral dose-response data

for acute, intermediate, and/or chronic duration.''

These priority data needs are filled if minimal risk levels (MRLs)

have been derived in the updated ATSDR toxicological profile since the

finalization of the priority data needs document. However, in certain

cases where the database (from which an MRL is derived) is sparse, a

data need may still be identified in the toxicological profile to

increase the confidence in the MRL.

2. Priority data need, ``Exposure levels in humans.''

This priority data need is considered filled if there are reference

range data (e.g., National Health and Nutrition Examination Survey

[NHANES]) or generally agreed upon background population levels AND if

there are current and adequate biomonitoring data for exposed

populations associated with health effects (from published or ongoing

studies).

This priority data need is reclassified as a data need if only one

of the following 2 criteria is met: (1) There are reference range data

or generally agreed upon background population levels OR (2) if there

are current and adequate biomonitoring data for exposed populations

associated with health effects (from published or ongoing studies).

3. Priority data need ``Mechanism of toxic action.''

This priority data need is considered filled if there is scientific

consensus indicating that the mechanism(s) of toxic action is well

characterized.

This priority data need is reclassified as a data need if an

updated toxicological profile contains relevant new (peer reviewed and

publicly available) studies since the finalization of the priority data

needs document; however, the database may not be sufficient to achieve

scientific consensus on the mechanism of toxic action.

Based on the above criteria, the status of the research needs for

the first set of 38 priority substances was evaluated (Table 1). To

date, 14 priority data needs and 2 data needs have been filled, 26

priority data needs have been reclassified as data needs, and 2

additional priority data needs (Table 1, vinyl chloride, PDN ID #4B and

4E) and 1 data need (Table 1, PCBs, PDN ID #7H) are considered

conditionally filled pending ATSDR peer review of the final reports.

Update of Activities in the SSARP

An update of the activities associated with the mechanisms for

implementing the ATSDR Substance-Specific Applied Research Program

(SSARP) is discussed below.

A. TSCA/FIFRA

In developing and implementing the SSARP, ATSDR, NTP, and EPA

identified priority data needs for substances on the TSCA inventory of

mutual interest to the federal programs. These data needs are being

addressed through a program of toxicologic testing under TSCA according

to established procedures and guidelines. On several occasions when

ATSDR identified priority data needs for oral exposure, other agencies

needed inhalation data. In response, ATSDR is considering proposals to

conduct inhalation studies in conjunction with physiologically based

pharmacokinetic (PBPK) studies in lieu of oral bioassays. ATSDR expects

that inhalation data derived from these studies can be used with PBPK

modeling to address its oral toxicity data needs. Currently, an EPA/

ATSDR test rule, under development, includes 7 ATSDR substances, i.e.,

benzene, chloroethane, cyanide (including hydrogen cyanide and sodium

cyanide), methylene chloride, tetrachloroethylene, trichloroethylene,

and toluene, and addresses 15 priority data needs (Table 3). The test

rule was reviewed by ATSDR and is undergoing EPA final review. It will

be available for public comment in the near future.

TASARC has established an interagency task force on metals and has

recently conducted a survey to assess federal agencies' needs for

testing metals. Currently, the task force has agreed to examine at

least 7 metals included in the ATSDR's SSARP (arsenic, beryllium,

chromium, manganese, mercury, nickel, and selenium, associated with 22

priority data needs) (Table 3). The EPA will solicit testing proposals

for these metals and pursue test rule development for these metals at a

later date.

B. Private-Sector Voluntarism

As part of the SSARP, on February 7, 1992, ATSDR announced a set of

proposed procedures for conducting voluntary research (57 FR 4758).

Revisions based on public comments were published on November 16, 1992

(57 FR 54160). Private-sector organizations were encouraged to

volunteer to conduct research to address specific priority data needs.

ATSDR currently has memoranda of understanding (MOUs) in place with

the General Electric Company (GE), the Halogenated Solvents Industry

Alliance (HSIA), and the Chemical Manufacturers Association (CMA)

(Table 3). Through the voluntary research efforts of these

organizations, 12 research needs for two classes of substances

(polychlorinated biphenyl compounds [PCBs] and volatile organic

compounds, including methylene chloride, tetrachloroethylene,

trichloroethylene, and vinyl chloride) are being addressed (Table 3).

Recently, the agency received a study protocol from the Counselors

for Management, Inc., on behalf of a spectrum of the zinc industry

which is considering to conduct research to address ATSDR's priority

data needs for zinc. This represents the first study proposed by a

private-sector organization to address priority data needs for a metal.

Voluntary research covered under the three existing MOUs is described

next.

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General Electric Company

In 1995, ATSDR entered into an MOU with GE. This marked the first

time a private-sector organization had volunteered to conduct research

to address data needs identified in ATSDR's SSARP. The MOU with GE

covers two studies on PCBs: (1) ``An assessment of the chronic toxicity

and oncogenicity of Aroclors 1016, 1242, 1254, and 1260 administered in

diet to rats,'' including ``PCB congener analyses,'' and (2)

``Metabolite detection as a tool for determining naturally occurring

aerobic PCB biodegradation.'' While the above studies do not address

ATSDR's priority data needs for PCBs, they do address other agency

research needs for these substances.

The agency accepted the final report for the first study (chronic

toxicity and oncogenicity) in October 1997. The study provided an in-

depth understanding of the relative toxicity of the prevalent

commercial mixtures of PCBs (Aroclor 1016, Aroclor 1242, Aroclor 1254,

and Aroclor 1260) after long-term exposures. The investigators found

exposure-related toxicity for all four Aroclors. Furthermore, the study

includes characterization of PCB composition, tissue accumulation, and

correlations with tumorigenicity in chronically dosed rats. With regard

to the second GE study (aerobic PCB biodegradation), also covered under

the MOU, the final report is being evaluated by ATSDR's peer reviewers.

The acceptance of the final report will be based on the recommendations

of the reviewers and GE's satisfactory response to the reviewers'

comments.

Halogenated Solvents Industry Alliance (HSIA)

In 1995, ATSDR entered into an MOU with HSIA covering studies to

address three priority toxicity data needs for methylene chloride. The

studies, ``Addressing priority data needs for methylene chloride with

physiologically based pharmacokinetic modeling,'' evaluated acute- and

subchronic-duration toxicity via oral exposures and developmental

toxicity via oral exposure. The data were obtained by using

physiologically based pharmacokinetic modeling.

The final report for these studies, the first one to be completed

under the voluntary research program, was accepted by the agency in

February 1997. The HSIA studies indicated that adverse health effects

on the central nervous system, liver, and the development of newborns

may occur if people drink water containing high concentrations of

methylene chloride (565 to 6,170 milligrams methylene chloride per

liter of water). These amounts are much larger than what most people

are exposed to in the environment. However, these amounts approach

levels found at industrial sites and in waste waters (ATSDR's

Toxicological Profile for Methylene Chloride, 1993). HSIA has also

proposed to conduct an immunotoxicity assessment for methylene chloride

via inhalation exposure. The agency expects to receive a study protocol

from HSIA for peer review in the near future.

In addition, ATSDR and HSIA are continuing negotiation to expand

the existing MOU to include research on trichloroethylene and

tetrachloroethylene.

Chemical Manufacturers Association (CMA)

In 1996, ATSDR entered into an MOU with CMA covering two studies,

``Vinyl chloride: Combined inhalation two-generation reproduction and

developmental toxicity study in CD rats.'' Recently, the ATSDR peer

review of the final report on the developmental toxicity study was

completed. The final report for the reproductive toxicity study is

undergoing ATSDR peer review. Acceptance of the final reports is based

on the reviewers' recommendations and CMA's satisfactory response to

the reviewers' comments.

C. CERCLA-Funded Research (Minority Health Professions Foundation

Research Program)

During FY 1992, ATSDR announced a $4 million cooperative agreement

program with the Minority Health Professions Foundation (MHPF) to

support substance-specific investigations. A not-for-profit 501(c)(3)

organization, the MHPF comprises 11 minority health professions

schools. Its primary mission is to research the health problems that

disproportionately affect poor and minority citizens. The purpose of

this cooperative agreement is to address substance-specific data needs

for priority hazardous substances identified by ATSDR. In addition,

this agreement strengthens the environmental health research

opportunities for scientists and students at MHPF member institutions

and enhances existing disciplinary capacities to conduct research in

toxicology and environmental health.

In the first 5-year project period that concluded during FY 1997, 9

priority data needs for 21 priority hazardous substances and 22 data

needs for these and other substances were addressed. The MHPF has

developed a report, ``Environmental Health and Toxicology Research

Program: Meeting Environmental Health Challenges Through Research,

Education, and Service,'' that describes the research findings and

other successes from the first 5 years of the program. New research

initiated in the second 5-year project period includes studies to

address 10 additional priority data needs for chlordane, 1,2-dibromo-3-

chloropropane, di-n-butyl phthalate, lead, manganese, the polycyclic

aromatic hydrocarbons (PAHs), and zinc, and another 8 data needs.

To date, the MHPF activities have resulted in the publication of 21

manuscripts in peer-reviewed journals. Findings from this program were

presented at a symposium held in April 1997, in New Orleans. Also,

these and other research findings from the program were featured in a

special session during the 1998 annual meeting of the Society of

Toxicology in Seattle. The institutions receiving awards and their

respective research projects are listed in Table 3.

D. National Toxicology Program (NTP)

ATSDR maintains an interagency agreement (IAG) with NTP to conduct

toxicologic testing of substances identified at NPL sites. The studies

determine levels of exposure that present a significant risk to humans

of acute, subchronic, and chronic health effects. Often these studies

include an assessment of the substance's ability to cause cancer,

reproductive toxicity, and birth defects. The results of these studies

are used by regulatory agencies, various environmental and industrial

groups, and ATSDR to improve its ability to conduct public health

assessments at NPL sites.

Under this agreement, one toxicity priority data need identified in

the SSARP (immunotoxicology study of carbon tetrachloride) was filled

(Table 1). Research efforts to address reproductive toxicity data needs

for chlordane, endrin, and heptachlor, the bioavailability of PCBs in

soil, and dose-response data for di-n-butyl phthalate are also ongoing

(Table 3).

During FY 1993, the existing IAG was modified to include toxicity

studies of ATSDR's priority hazardous substances via application of

structure-activity relationship (SAR) techniques, PBPK modeling, and

functional toxicity testing. The ATSDR-supported NTP studies in these

areas are ongoing.

E. Great Lakes Human Health Effects Research Program

Some of the priority data needs identified in the SSARP have been

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independently identified as research needs through the ATSDR Great

Lakes Human Health Effects Research Program, a separate research

program.

In support of the Great Lakes Critical Programs Act of 1990, ATSDR

announced in FY 1992 the availability of $2 million for a grant program

to conduct research on the potential for short-and long-term adverse

health effects from consumption of contaminated fish from the Great

Lakes basin. Research undertaken through this program is intended to

build on and amplify the results of past and ongoing fish consumption

research in the Great Lakes basin. The ATSDR-supported research

projects focus on known high-risk populations to further define the

human health consequences of exposure to persistent toxic substances

(PTSs) identified in the Great Lakes basin. These at-risk populations

include sport anglers, Native Americans, pregnant women, fetuses and

nursing infants of mothers who consume contaminated Great Lakes fish,

infants and children, the elderly, and the urban poor.

To date, the research activities of the ATSDR Great Lakes research

program have resulted in 22 manuscripts in peer-reviewed journals. An

additional 13 manuscripts have been accepted for publication and will

soon be in press. Research findings from this program have been

presented at 8 international conferences and various scientific

meetings and symposia.

Currently, 13 priority data needs and 1 data need for 24 priority

hazardous substances (including 15 PAHs) identified in the SSARP are

being addressed through this program. The institutions receiving awards

and their respective studies are listed in Table 3.

F. Other ATSDR Programs

In its role as a public health agency addressing environmental

health, ATSDR may collect human data to validate substance-specific

exposure and toxicity findings. The need for additional information on

levels of contaminants in humans has been identified and remains as a

priority data need for 37 of the first set of 38 priority substances

(Table 1). Similarly, this priority data need has been identified for

all 12 of the second set of 12 priority substances. ATSDR will obtain

this information through exposure and health effects studies, and

through establishing and using substance-specific subregistries of

people within the agency's National Exposure Registry who have

potentially been exposed to these substances.

The list of 50 priority hazardous substances in the SSARP was

forwarded to ATSDR's Exposure and Disease Registry Branch (EDRB),

Division of Health Studies, for consideration as potential candidates

for subregistries of exposed persons, based on criteria described in

its 1994 document, ``National Exposure Registry: Policies and

Procedures Manual (Revised),'' Agency for Toxic Substances and Disease

Registry, Public Health Service, U.S. Department of Health and Human

Services, Atlanta, Georgia, NTIS Publication No. PB95-154571. To date,

of the first set of 38 priority substances in the SSARP, ATSDR has

selected benzene, chromium, and trichloroethylene as primary

contaminants to establish subregistries in the National Exposure

Registry. However, aldrin/dieldrin, beryllium, carbon tetrachloride,

chloroethane, chloroform, cyanide, p,p'-DDT, DDE, DDD, di(2-

ethylhexyl)phthalate, mercury, methylene chloride, nickel, PAHs, PCBs,

selenium, tetrachloroethylene, toluene, vinyl chloride, and zinc remain

in the candidate pool and therefore continue to be classified as

priority data needs. They will be considered for selection as primary

contaminants during each selection process (Table 1). Arsenic, cadmium,

and lead are not considered to be in the pool of candidate substances

for an exposure registry at this time, and therefore, are not

considered priority data needs. This decision will be reevaluated as

more information on the chemicals and exposure sites become available.

Regarding the second set of 12 priority substances, all of them

were included in the candidate pool for establishment of exposure

subregistries (i.e., priority data needs, published in the 1996 Federal

Register Notice [61 FR 14430]). However, during a recent reevaluation

of the database, manganese was removed from the candidate pool, and

therefore, this priority data need for manganese has been reclassified

as a data need, and is not included in Table 2.

The results of the research conducted via the SSARP will be used

for public health assessments and to reassess ATSDR's substance-

specific priority data needs. The agency expects to provide an update

on the status of this research program every three years.

Dated: January 11, 1999.

Georgi Jones,

Director, Office of Policy and External Affairs, Agency for Toxic

Substances and Disease Registry.

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[FR Doc. 99-971 Filed 1-14-99; 8:45 am]

BILLING CODE 4163-70-C