[Federal Register Volume 61, Number 239 (Wednesday, December 11, 1996)]
[Rules and Regulations]
[Pages 65183-65185]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-31429]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 131

[FRL-5663-5]


National Toxics Rule: Remand of Water Quality Criteria for Dioxin 
and Pentachlorophenol to EPA for Response to Comments

AGENCY: U.S. Environmental Protection Agency.

ACTION: Notice of availability of US EPA response to comments.

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SUMMARY: In this document, the U.S. Environmental Protection Agency 
(``EPA'') is publishing a document entitled ``Response to Comments from 
American Forest and Paper Association (``AFPA'') on Two of the Exposure 
Assumptions Used by EPA in Developing the Human Health Water Quality 
Criteria for Dioxin and Pentachlorophenol''. AFPA challenged EPA's 
promulgation of human health water quality criteria for dioxin and 
pentachlorophenol. The District Court remanded these criteria to EPA 
for an adequate response to AFPA's comments regarding two exposure 
assumptions used by EPA in developing those criteria: an assumption 
that daily water consumption is 2 liters, and an assumption that all 
consumed fish are contaminated at criteria levels. EPA has prepared a 
response in accordance with the court's order, and is publishing that 
response in this document.

FOR FURTHER INFORMATION CONTACT: Denis R. Borum, Office of Science and 
Technology, Office of Water (4304), USEPA, 401 M Street, SW., 
Washington, D.C. 20460, (202) 260-8996.

SUPPLEMENTARY INFORMATION: In November 1991, EPA proposed chemical-
specific, numeric criteria for priority toxic pollutants, including 
dioxin and pentachlorophenol, necessary to bring all States into 
compliance with the requirements of section 303(c)(2)(B) of the Clean 
Water Act. (The ``National Toxics Rule'' or ``NTR'', 56 FR 58420; 
codified at 40 CFR 131.36.) AFPA commented on a number of aspects of 
the proposal, including the exposure assumptions used in EPA's water 
quality criteria methodology. The NTR was promulgated in December 1992 
(57 FR 60848; codified at 40 CFR 131.36). AFPA challenged the rule as 
arbitrary and capricious in violation of the Administrative Procedure 
Act, 5 U.S.C. 551 et seq. (Civil Action No. 93-CV-0694 (RMU), DCDC.) On 
September 4, 1996, the court issued an order remanding the human health 
criteria for dioxin and pentachlorophenol to EPA for ``an adequate 
response to AFPA's comments'' regarding two of the exposure assumptions 
used by EPA in developing the criteria. These assumptions are that 
daily water consumption is 2 liters, and that all consumed fish are 
contaminated at the criteria levels.
    The court directed EPA to respond to AFPA's comments on these two 
issues by December 13, 1996, or the human health criteria for dioxin 
and pentachlorophenol will be vacated automatically. This notice 
publishes EPA's response to AFPA's comments. Under the order, AFPA has 
60 days from the publication of EPA's response to re-open the 
litigation; upon expiration of the 60 days, the action will stand 
dismissed with prejudice.
    In accordance with section 553 of the Administrative Procedure Act, 
EPA has determined that there is good cause not to solicit public 
comment on this notice. In this notice, the Agency is simply responding 
to comments on the proposed NTR and such responses are not subject to 
further public comment. Moreover, the public has had ample opportunity 
to comment on the exposure assumptions addressed in this notice since 
the assumptions have been reflected in a number of Agency regulatory 
actions. For these reasons, EPA finds further public comment to be 
unnecessary.

    Dated: December 5, 1996.
Robert Perciasepe,
Assistant Administrator for Water.

Response to Comments From the American Forest and Paper Association on 
Two Exposure Assumptions Used by EPA To Develop Human Health Water 
Quality Criteria for Dioxin and Pentachlorophenol

Background

    The purpose of the Clean Water Act (``CWA'') is to protect the 
nations waters, on which public health and the environment depend. 
Toward this end, the CWA requires those discharging into surface waters 
of the United States to have permits that limit the amount of 
pollutants discharged. To set such limits, ``criteria'' are established 
for each pollutant at a level necessary to preserve or achieve the uses 
designated for particular waterbodies by the States. In other words, 
for waterbodies designated as drinking water supplies, the criteria 
should assure that people can safely drink the water. Where waterbodies 
are to be used for fishing, swimming or recreation, the criteria should 
assure that people can safely eat fish that are taken from those 
waters, and safely use

[[Page 65184]]

the waters for other designated purposes. These criteria, intended to 
protect public health, are referred to as ``human health criteria''.
    Human health criteria are derived to establish quantitative 
estimates of chemicals which, if not exceeded, will protect the general 
population from adverse health impacts from exposure to contaminated 
surface water. There are two routes of human exposure: water 
consumption and fish consumption. In order to develop the criteria, EPA 
needed to determine appropriate exposure assumptions for these 
pathways. In 1980, EPA announced its methodology for establishing human 
health criteria. 45 FR 79318 (Nov. 28, 1980). To predict the effects of 
low doses of the pollutant on a hypothetical person over a 70-year 
lifetime, EPA assumed the exposed individual is a male who weighs 70-
kilograms and who on a daily basis consumes an average of 6.5 grams of 
fish and shellfish and 2 liters of water. Id, at 79323-24. EPA also 
assumed for purposes of the methodology that the consumed water and 
fish are contaminated at the criteria levels. Id., at 79323.

Issue 1: EPA's Estimate of Water Intake as 2 Liters per Day

    As noted above, in order to derive human health criteria, EPA 
needed to make assumptions concerning daily exposure to pollutants in 
surface water from two primary routes: water consumption and fish 
consumption. EPA has assumed an average daily water consumption of 2 
liters. The Agency recognizes that a number of other drinking water 
consumption rates have been suggested. Having reviewed those studies, 
EPA's policy judgment continues to be that an assumed daily consumption 
of 2 liters is reasonable to provide the margin of safety needed to 
protect most people and thereby meet the objectives of the CWA. EPA is 
not required, by the CWA or regulation, to base its assumed water 
consumption on ``average ingestion'' in statistical terms. Rather, as 
EPA explained in the proposed NTR, the assumed water consumption rate 
is based on an ``approximate'' national average. (56 FR 58436), i.e., 
the approximate national average may be a starting point not an end 
point. Also, both the Agency and the National Academy of Sciences 
(``NAS'') have indicated that policy reasons are appropriate 
considerations in adopting ``average'' drinking water consumption 
rates. Since 1980, EPA has on several occasions reviewed and publicly 
addressed the rationale for its water consumption value, but to the 
extent that questions remain as to the basis for the assumption, EPA 
here further explains that rationale.
    The Agency's 1980 methodology for deriving human health criteria 
assumed a water consumption of 2 liters per day. EPA cited a study done 
by the NAS in support of this assumption. The NAS study was undertaken 
to meet the needs expressed in the 1974 Safe Drinking Water Act 
(``SDWA''). Under the SDWA, EPA was required to establish federal 
standards for protection from harmful contaminants in the drinking 
water supplies of the nation. Congress directed EPA to arrange with the 
NAS to study the adverse effects on health attributable to contaminants 
in drinking water. In 1977, NAS produced a multi-volume study entitled 
Drinking Water and Health, National Academy of Sciences, Washington, 
D.C. 1977. In this study, NAS considered 2 liters to be the average 
amount of water consumed per day. While noting that the average per 
capita water consumption of the U.S. population, as calculated from a 
survey of nine different literature sources, was 1.63 liters per day, 
NAS adopted 2 liters per day as representing the ``intake of the 
majority of water consumers''. Id. at 11. EPA adopted 2 liters per day 
as the drinking water exposure for its human health criteria 
methodology, understanding that it included a margin of safety that 
would ensure that most of the population would be protected.
    In its comments on the proposed NTR, AFPA argued that the assumed 2 
liters per day water consumption rate was overly conservative:

    In a paper recently accepted for publication in Risk Analysis 
(Exhibit 9) * * * (the) analysis demonstrated that the 50th 
percentile intake of ``tap water'' * * * was slightly less than one 
liter per day. * * * ChemRisk recently analyzed similar water 
consumption data and came up with a similar figure for ``tap water'' 
consumption--1.2 liters per day. (Exhibit 2) Since an individual 
exposed to contaminated surface water would at most only be exposed 
to that contamination in the ``tap water'' he consumes, and not in 
the moisture content inherent in foods that he purchases. * * * the 
two liter per day assumption EPA has used overstates by a factor of 
2 the potentially contaminated water that an average individual 
might consume. AFPA Comments on Proposed Rule, Dec. 19, 1991, pp. 
59-60.

    The ChemRisk analysis states that EPA's 2.0 liters per day value is 
based on the daily ration of water required by US Army field personnel; 
ChemRisk questions whether this value is appropriate for a general 
population with access to other beverages and that does not engage in 
as much physical exertion and is not as exposed to the outdoors. 
ChemRisk reviewed several studies that show the average adult 
consumption rate for liquids ranges from 0.4 to 2.2 L/day. Based on a 
study showing that approximately 60% of the total dietary fluid intake 
is water, ChemRisk concludes that if a total fluid consumption rate of 
2 liters per day is reasonable, then 60% of that consumption rate or 
1.2 liters per day is water. (pp. 5-1 to 5-2)
    EPA is familiar with the studies, including those cited by AFPA, 
that estimate average consumption of water to be less than 2 liters per 
day. Indeed, in 1990, EPA conducted its own analysis of data that 
suggested that the average water consumption rate across the U.S. adult 
population is 1.4 liters per day. ``Exposure Factors Handbook'', EPA 
600/8-89/043, at 2-6 (AR VA-103). However, while noting that the 
scientific literature suggests a daily rate of 1.4 liters, EPA made 
clear that ``[p]olicy or precedent reasons may support  the  continued  
use  of  the  2.0  L/day [figure] as the average adult drinking water 
consumption rate.'' This analysis further indicates that consumption of 
2 liters per day covers about 90 percent of the population; the 
remaining 10 percent of the population consumes more than a daily 
average of 2 liters. In this analysis, 2 liters per day is 
characterized as a reasonable worst-case water consumption rate for 
adults. Since EPA's purpose in selecting 2 liters as an average daily 
water consumption rate was to provide a margin of safety sufficient to 
protect most people--to the extent that 2 liters per day is protective 
of approximately 90 percent of the population--using 2 liters per day 
as the assumed water consumption rate for the NTR is consistent with 
EPA's approach in setting human health criteria.
    In a 1992 SDWA rulemaking that established health-based contaminant 
levels for numerous pollutants in drinking water (57 FR 31,776), the 
issue of water consumption estimates was re-examined yet again. In the 
SDWA rulemaking, the Chemical Manufacturers Association (``CMA'') 
submitted comments (which mirror those submitted by AFPA in the 
contemporaneous NTR rulemaking) objecting to EPA's use of 2 liters per 
day to set drinking water standards. CMA recommended instead the 1.4 
liters per day estimate in EPA's Exposure Factors Handbook. In response 
to CMA's comments, EPA acknowledged that the 1.4 liters per day 
estimate is ``an overall average of a number of studies'' but rejected 
using that value since some of the studies did not necessarily consider 
indirect water consumption (such as use in cooking) and therefore may 
not account for all exposures related to the

[[Page 65185]]

occurrence of contaminants in drinking water. EPA reiterated that the 2 
liters per day assumption was a more appropriate value ``in order to be 
conservative and allow for an adequate margin of safety.'' Id. at 
31787. EPA further noted that the Exposure Factors Handbook considered 
2 liters per day a reasonable worst case estimate.
    The Agency's rationale and conclusion in the drinking water 
regulation is equally applicable to the NTR. Therefore, EPA included 
the Federal Register notice (Id. 31787-31788) containing EPA's response 
to CMA's comments on the 2 liters per day figure in the record for the 
NTR rulemaking. In the NTR, an assumption of water consumption of 2 
liters per day provides a sufficient margin of safety to ensure that 
most people can safely drink from waterbodies designated as drinking 
water sources.
    In sum, AFPA disagrees with EPA's choice of methodology and desired 
level of health protection in deriving an estimate of assumed water 
consumption. EPA is not required under the CWA to base its water 
consumption estimate on ``average ingestion'' in statistical terms. In 
order to meet the objectives of the CWA, EPA believes that its assumed 
water consumption must include a margin of safety so that the general 
population is protected. The NAS adopted a water consumption figure of 
2 liters per day in its study of drinking water and public health as 
representing the consumption of the majority of water consumers. EPA 
has reviewed the subsequent studies of water consumption, but continues 
to believe that 2 liters per day is appropriate for ensuring protection 
of public health under the CWA.

Issue 2. EPA's Assumption That All of the Fish Consumed Is Contaminated 
at the Criteria Level

    In developing a methodology for deriving human health criteria, EPA 
made assumptions about exposure to contamination from eating fish taken 
from surface waters. The purpose of the assumptions was to ensure that 
if the criteria were met in a waterbody designated for fishing, most 
people could safely eat fish from that waterbody. In addition to the 
assumption in the methodology that the hypothetical man has an average 
daily consumption of 6.5 grams of fish, EPA assumes that all of that 
fish is taken from water with pollutants present at the criteria level.
    It is EPA's view that to ensure that people can safely eat fish 
from waters designated for fishing, it is necessary to assume that all 
of the consumed fish is taken from waterbodies at the criteria level. 
EPA recognizes that there are differences in fishing patterns and the 
degree to which fish bioaccumulate contaminants from the water. 
However, it is EPA's judgment that this assumption regarding fish 
contamination is necessary to derive criteria that are sufficiently 
protective to meet the objectives of the CWA.
    AFPA commented that this assumption overstates the actual expected 
exposure to a contaminant:

    Another source of overestimation of exposure comes from the 
implicit assumption that each portion of freshwater fish consumed by 
an individual will have the maximum concentration of the subject 
contaminant * * * This assumption is obviously an overstatement, 
since not all fish (presumably very few of them, in fact) will have 
been exposed to ambient water which is just barely achieving the 
water quality standard. Likewise, if the water quality standards are 
being met, it would only be on rare occasions that the water 
consumed will have a concentration as high as the water quality 
standard allows. By definition, if the water quality standard is 
implemented, ambient concentrations of the pollutant will normally 
be less. In addition, depending on the dilution calculations (if 
any) used in implementing the water quality standard, there may be 
little or no portion of the stream where the concentration of the 
pollutant is ever as high as the water quality standard allows (due 
to dilution and the use of low stream flows * * * EPA has very 
recently made this point forcefully in briefs and argument in the 
Eastern District of Virginia in NRDC, et al. v. U.S. EPA, No. 
3:91CV0058. [cite omitted]. EPA has noted that FDA's analysis of 
risk from eating dioxin-contaminated fish in the Great Lakes assumed 
that * * * 90 percent of the fish an individual consumed would show 
no measurable contamination or would be taken from uncontaminated 
areas. (cite omitted). AFPA Comments on Proposed National Toxics 
Rule, December 19, 1991, pp. 60-61.

    Two exhibits to AFPA's comments were prepared for the National 
Council of the Paper Industry for Air and Stream Improvement. Exhibit 2 
discusses studies of fish consumption of anglers in New York and Maine, 
and Exhibit 4 addresses exposure to dioxin from the consumption of fish 
caught in fresh waters impacted by certain pulp mills. Both reports 
conclude that it is unlikely that all of the fish consumed by sport 
anglers come from only one waterbody or from impacted waters. The 
dioxin report notes, however, that no data are available on the number 
of waterbodies fished by members of the general population or sport 
fishermen over a course of time.
    In its methodology, EPA assumes that all fish consumed by the 
hypothetical exposed individual are contaminated at the maximum 
concentration level that is ``safe'' (i.e., the criteria level). This 
is the same assumption that EPA makes as to water consumption, and the 
Agency's rationale supporting that assumption is equally applicable to 
fish consumption.
    AFPA offers examples of situations which, it contends, make it 
unlikely that individuals will be exposed at the criteria level. EPA is 
aware that levels of actual exposure to contamination from consuming 
fish will vary depending on a number of factors. Daily fish consumption 
may be both greater than and less than 6.5 grams. As EPA noted in the 
proposed NTR, the exposure assumptions are based on approximate 
national averages, but ``considerably understate the exposure that 
would occur for certain segments of the population that have high fish 
consumption or depend on fish consumption for subsistence.'' Id. at 
58,436.
    AFPA's exhibits note that sport fishing patterns may differ among 
communities. Fishermen with access to a number of different waterbodies 
may very well fish in several places and the levels of contamination 
may differ among those waterbodies. Further, different species of fish 
bioaccumulate pollutants at different rates. There are many 
circumstances that may be relevant to fish consumption in different 
communities and the level of contamination of those fish. However, 
whether people fish from a number of locations, or whether some 
waterbodies are not as contaminated as others does not demonstrate that 
EPA's assumption is invalid. EPA must develop national criteria (that 
States may modify) that must be protective of the general population. 
Neither AFPA nor other commenters provided EPA with evidence sufficient 
to allow the Agency to use a less conservative assumption.
    It continues to be EPA's view that in order to develop criteria 
that are sufficiently protective, it is necessary to assume that all 
consumed fish are taken from waters at the criteria level. By deriving 
criteria based on that assumption, EPA is better able to ensure that 
people can safely eat fish from waters designated for fishing.
    The local circumstances that AFPA reports are best addressed by the 
States which have chief responsibility for implementing the CWA. States 
can modify or adapt EPA's recommended human health criteria to reflect 
just such local environmental conditions, and EPA encourages them to do 
so. (See 57 FR 60888, Dec. 22, l992).

[FR Doc. 96-31429 Filed 12-10-96; 8:45 am]
BILLING CODE 6560-50-P