(F) Childhood exposure was considered for all noncarcinogens.
Consumption rates for fish and shellfish were estimated as 5.6 grams
per child per day, and drinking water consumption rates were estimated
as 0.64 liters per child per day. A child body weight was estimated
at 15 kilograms. Both the water consumption rate and body weight are
age-adjusted for a six-year-old child. The consumption rate for fish
and shellfish for children is from Table 10-61 of EPA's 1997 Exposure Factors Handbook (EPA/600/P-95/002Fa-c).
(G) Numerical human health criteria were derived in
accordance with the general procedures and calculations in the EPA
guidance documents entitled Technical Support
Document for Water Quality-based Toxics Control (EPA/505/2-90-001); Guidance Manual for Assessing Human Health Risks
from Chemically Contaminated Fish and Shellfish (EPA/503/8-89-002);
and Methodology for Deriving Ambient Water
Quality Criteria for the Protection of Human Health (2000) (EPA-822-B-00-004).
(H) If a calculated criterion to prevent contamination
of drinking water and fish to ensure they are safe for human consumption
(Column A in Table 2 of paragraph (1) of this subsection) was greater
than the applicable maximum contaminant level (MCL) in Chapter 290
of this title (relating to Public Drinking Water), then the MCL was
used as the criterion.
(I) If the concentration of a substance in fish tissue
used for these calculations was greater than the applicable United
States Food and Drug Administration Action Level for edible fish and
shellfish tissue, then the acceptable concentration in fish tissue
was lowered to the Action Level for calculation of criteria.
(4) Human health criteria for additional toxic materials
are adopted by the commission as appropriate.
(5) Specific human health concentration criteria for
water are applicable to water in the state that has sustainable fisheries
or designation or use as a public drinking water supply or as a sole-source
drinking water supply except within mixing zones and below stream
flow conditions as specified in §307.8 of this title. The following
waters are considered to have sustainable fisheries:
(A) all designated segments listed in Appendix A of §307.10
of this title, unless specifically exempted;
(B) perennial streams and rivers with a stream order
of three or greater, as defined in §307.3 of this title (relating
to Definitions and Abbreviations);
(C) lakes and reservoirs greater than or equal to 150
acre-feet or 50 surface acres;
(D) all bays, estuaries, and tidal rivers; and
(E) any other waters that potentially have sufficient
fish production or fishing activity to create significant long-term
human consumption of fish.
(6) Waters that are not considered to have a sustainable
fishery, but that have an aquatic life use of limited or greater,
are considered to have an incidental fishery. Consumption rates assumed
for incidental fishery waters are 1.75 grams per person per day. Therefore,
numerical criteria applicable to incidental fishery waters are ten
times the criteria listed in Column B in Table 2 of paragraph (1)
of this subsection.
(7) Specific human health criteria are applied as long
term average exposure criteria designed to protect populations over
a life time. Attainment measures for human health are addressed in §307.9
of this title.
(8) For toxic materials of concern where specific human
health criteria are not listed in Table 2 of paragraph (1) of this
subsection, the following provisions apply:
(A) For known or suspected carcinogens (as identified
in EPA's IRIS database), a cancer risk of 10-5 (1
in 100,000) is applied to the most recent numerical criteria adopted
by the EPA and published in the Federal Register.
If an MCL or equivalent agency guideline for protection of
drinking water sources is less than the resulting criterion, then
the MCL applies to public drinking water supplies in accordance with
paragraph (3)(H) of this subsection.
(B) For toxic materials not defined as carcinogens,
the most recent numerical criteria adopted by the EPA and published
in the Federal Register are applicable.
If an MCL or equivalent agency guideline for protection of drinking
water sources is less than the resulting criterion, then the MCL applies
to public drinking water supplies in accordance with paragraph (3)(H)
of this subsection.
(C) In the absence of available criteria, numerical
criteria may be derived from technically valid information and calculated
in accordance with the provisions of paragraph (3) of this subsection.
(9) Numerical criteria for bioconcentratable pollutants
are derived in accordance with the general procedures in the EPA guidance
document entitled Assessment and Control
of Bioconcentratable Contaminants in Surface Water (March 1991).
The commission may develop discharge permit limits in accordance with
the provisions of this section.
(10) Numerical human health criteria are expressed
as total recoverable concentrations for nonmetals and selenium and
as dissolved concentrations for other metals and metalloids.
(11) Additional site-specific factors may indicate
that the numerical human health criteria listed in Table 2 of paragraph
(1) of this subsection are inappropriate for a particular water body.
These factors are applied as a site-specific standards modification
in accordance with §307.2(d) of this title. The application of
site-specific criteria must not impair an existing, attainable, presumed,
or designated use or affect human health. Factors that may justify
a temporary variance or site-specific standards amendment include
the following:
(A) background concentrations of specific toxics of
concern in receiving waters, sediment, or indigenous biota;
(B) persistence and degradation rate of specific toxic
materials;
(C) synergistic or antagonistic interactions of toxic
substances with other toxic or nontoxic materials;
(D) technological or economic limits of treatability
for specific toxic materials;
(E) bioavailability of specific toxic substances of
concern;
(F) local water chemistry and other site-specific conditions
that may alter the bioconcentration, bioaccumulation, or toxicity
of specific toxic substances;
(G) site-specific differences in the bioaccumulation
responses of indigenous, edible aquatic organisms to specific toxic
materials;
(H) local differences in consumption patterns of fish
and shellfish or drinking water, but only if any changes in assumed
consumption rates are protective of the local population that frequently
consumes fish, shellfish, or drinking water from a particular water
body; and
(I) new information concerning the toxicity of a particular
substance.
(e) Total toxicity.
(1) Total (whole-effluent) toxicity of permitted discharges,
as determined from biomonitoring of effluent samples at appropriate
dilutions, must be sufficiently controlled to preclude acute total
toxicity in all water in the state with the exception of small ZIDs
at discharge points and at extremely low streamflow conditions (one-fourth
of critical low-flow conditions) in accordance with §307.8 of
this title. Acute total toxicity levels may be exceeded in a ZID,
but there must be no significant lethality to aquatic organisms that
move through a ZID, and the sizes of ZIDs are limited in accordance
with §307.8 of this title. Chronic total toxicity, as determined
from biomonitoring of effluent samples at appropriate dilutions, must
be sufficiently controlled to preclude chronic toxicity in all water
in the state with an existing or designated aquatic life use of limited
or greater except in mixing zones at discharge points and at flows
less than critical low-flows, in accordance with §307.8 of this
title. Chronic toxicity levels may be exceeded in a mixing zone, but
there must be no significant sublethal toxicity to aquatic organisms
that move through the mixing zone.
(2) General provisions for controlling total toxicity.
(A) Dischargers whose effluent has a significant potential
for exerting toxicity in receiving waters as described in the Procedures to Implement the Texas Surface Water
Quality Standards (RG-194) as amended are required to conduct
whole effluent toxicity biomonitoring at appropriate dilutions.
(B) In addition to the other requirements of this section,
the effluent of discharges to water in the state must not be acutely
toxic to sensitive species of aquatic life, as demonstrated by effluent
toxicity tests. Toxicity testing for this purpose is conducted on
samples of 100% effluent, and the criterion for acute toxicity is
mortality of 50% or more of the test organisms after 24 hours of exposure.
This provision does not apply to mortality that is a result of an
excess, deficiency, or imbalance of dissolved inorganic salts (such
as sodium, calcium, potassium, chloride, or carbonate) that are in
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