Page 1174 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

1106 SECTION | XVI Feed and Water Contaminants

VetBooks.ir TABLE 80.3 (Continued) Upper Concentration Limit (mg/L)

Water System
Freshwater Aquatic Life Freshwater Marine Aquatic Life
Wildlife

Agency Canadian US EPA US EPA Canadian US EPA a
Chemical
Selenium 0.001 0.01 3 96-h
LC 50 , 0.01 mg/L
Sulfate
Zinc 0.030
Microorganisms 2000/dL
Fecal coliforms 2000/dL
a
Recommended concentration limits are expressed as the fraction of either lethal concentration- 50 (LC 50 ) or lethal dose-50 (LD 50 ). The concentration listed
thereafter is the maximum concentration considered acceptable.

United States (US EPA, (a), (b)), Canada (Health Canada, WATER CONSUMPTION TABLES
2012) and the World Health Organization (World Health
The dose of a water-borne contaminate may have to be
Organization, 2011). They are included in this chapter to
estimated in cases of suspected toxicoses and may be cal-
allow readers to compare standards for animals and
culated if the contaminant’s concentration in the water
humans. The adverse health effects listed in US EPA
and the amount of water consumed by the victims are
documents for each chemical are also listed in the table.
known. Contaminant concentration in the water may be
In the United States, legal limits called maximum con-
determined by analysis, but water consumption by the
taminant levels (MCLs) have been established for about
victims is rarely known with certainty.
90 contaminants. If contaminant concentrations in public
Water consumption varies by species, weather condi-
water supplies and certain private supplies are found to be
tion, diet, and state of health. All of those factors and
above applicable MCLs, then the water supplier must take
their interactions make the determination or estimation of
action to bring the contaminant concentration down below
minimal water requirements difficult if not impossible.
the MCL. Meanwhile, an alternate source of water that
Additionally, daily water requirements are not necessarily
meets the standards must be provided.
met solely by drinking water consumption.
In the United States, there are primary and secondary
Use water consumption data to calculate doses of
water standards for human drinking (US EPA, (a), (b)).
water-borne poisons, if such data are available. If not, use
Primary drinking water standards are legally enforceable, and
the data in Table 80.5, which was taken from the NAS
water providers cannot provide water that contains contami-
publication (NAS Subcommittee on Nutrient and Toxic
nants higher than their respective MCLs. Secondary standards
Elements in Water, 1974), to estimate water consumption.
are nonenforceable guidelines for contaminants that may
Those data should be modified for situations falling out-
cause cosmetic effects, such as skin or tooth discoloration, or
side of the defining parameters listed in the title.
unacceptable aesthetic effects, such as unacceptable taste of,
odor from or discoloration of the water.
Primary standards are established considering the RATIONALE FOR LIVESTOCK
adverse health effect caused by the contaminant and the RECOMMENDATIONS
dose at which such effects occur. A reference dose (RFD
or RfD) is estimated based upon the amount of the con- The rationales for the chemicals included in Table 80.2
taminant to which a person may be exposed on a daily livestock recommendations are included in the US EPA
basis that is not anticipated to cause the adverse health Proposed Criteria for Water Quality Volume (US EPA,
effect over a person’s life time. Consequently, the stan- 1973) 1 are summarized below. Information listed was
dards may not reflect the risk of adverse health effects in what was known at the time the recommendations were
animals, and care should be use applying them to water formulated and may not reflect current knowledge of the
intended for consumption by animals. effects of the chemicals. Our addenda are so noted.