Federal Register, Volume 75, Number 98, May 21, 2010, Pages 28463-28750 Page: 28,491

Federal Register/Vol. 75, No. 98/Friday, May 21, 2010/Rules and Regulations

substances that have a common
mechanism of toxicity."
EPA has not found silver nitrate to
share a common mechanism of toxicity
with any other substances, and silver
nitrate does not appear to produce a
toxic metabolite produced by other
substances. For the purposes of this
tolerance action, therefore, EPA has
assumed that silver nitrate does not
have a common mechanism of toxicity
with other substances. For information
regarding EPA's efforts to determine
which chemicals have a common
mechanism of toxicity and to evaluate
the cumulative effects of such
chemicals, see EPA's website at http://
D. Safety Factor for Infants and
1. In general. Section 408(b)(2)(C) of
FFDCA provides that EPA shall apply
an additional tenfold (10X) margin of
safety for infants and children in the
case of threshold effects to account for
prenatal and postnatal toxicity and the
completeness of the database on toxicity
and exposure unless EPA determines
based on reliable data that a different
margin of safety will be safe for infants
and children. This additional margin of
safety is commonly referred to as the
FQPA Safety Factor (SF). In applying
this provision, EPA either retains the
default value of 10X, or uses a different
additional safety factor when reliable
data available to EPA support the choice
of a different factor.
2. Prenatal and postnatal sensitivity
There is extensive data and analysis on
silver's toxicity in the historical data/
literature and regulatory advisories
established by other Federal Agencies,
which do not indicate an increased
susceptibility of children to the toxic
effects of silver. A National Toxicology
Program (NTP) developmental toxicity
study concluded that the NOAEL
recorded for developmental toxicity in
rats receiving gavages doses of silver
acetate was greater than 100 mg/kg/day
when the test material was administered
on gestation day 6 through 19. No
increase in susceptibility was apparent
in this study. Furthermore, silver nitrate
has been used for decades to treat
neonatal conjunctivitis. Finally, there is
no reason to believe that the effects that
are observed following the
administration of silver would warrant
additional safety factors for children.
The skin is the target organ and
deposition of silver should not be age
dependent. Moreover, because EPA
believes that the available
biomonitoring studies adequately
characterize variability in human

sensitivity, EPA is not applying an intra-

species uncertainty factor in deriving
the chronic RfD for silver.
3. Conclusion. Although EPA is not
applying an inter-species uncertainty
factor (because of reliance on human
data) or an intra-species uncertainty
factor (because human sensitivity has
been adequately characterized), EPA is
retaining the 10X FQPA safety factor in
assessing oral risk to address the fact
that the dose used to determine the
chronic RfD showed effects from silver
(argyria). In making its determination
regarding the appropriate safety factors
for evaluating the risk of silver, EPA
took into account that argyria is not a
toxic effect, there is no evidence of
increased sensitivity in the young from
exposure to silver, and the exposure
assessment for silver is very
E. Aggregate Risks and Determination of
Determination of safety section. EPA
determines whether acute and chronic
dietary pesticide exposures are safe by
comparing aggregate exposure estimates
to the acute population adjusted dose
(aPAD) and chronic population adjusted
dose (cPAD). For linear cancer risks,
EPA calculates the lifetime probability
of acquiring cancer given the estimated
aggregate exposure. Short-term,
intermediate-term, and chronic-term
risks are evaluated by comparing the
estimated aggregate food, water, and
residential exposure to the appropriate
point of departures (PODs) to ensure
that an adequate margin of exposure
(MOE) exists.
1. Acute risk. An acute aggregate risk
assessment takes into account acute
exposure estimates from dietary
consumption of food and drinking
water. No adverse effect resulting from
a single oral exposure was identified
and no acute dietary endpoint was
selected. Therefore, silver nitrate is not
expected to pose an acute risk.
2. Chronic risk. A chronic aggregate
risk assessment takes into account
exposure estimates from chronic dietary
consumption of food and from the use
of silver as a food contact sanitizer.
Using the exposure assumptions
described in this unit for chronic
exposure and the use limitations of not
more than 0.06% by weight in pesticide
formulations, the chronic dietary
exposure from food to silver nitrate is
20% of the cPAD for the U.S.
population and 63.8.6% of the cPAD for
children 1-2 years old, the most highly
exposed population subgroup.
3. Short-term risk. Short-term
aggregate exposure takes into account
short-term residential exposure plus

chronic exposure to food and water

(considered to be a background
exposure level).
Because no short-term adverse effect
was identified, silver nitrate is not
expected to pose a short-term risk.
4. Intermediate-term risk.
Intermediate-term aggregate exposure
takes into account intermediate-term
residential exposure plus chronic
exposure to food and water (considered
to be a background exposure level).
Because no intermediate-term adverse
effect was identified, silver nitrate is not
expected to pose an intermediate-term
5. Aggregate cancer risk for U.S.
population. The Agency has not
identified any concerns for
carcinogenicity relating to silver nitrate.
6. Determination of safety. Based on
these risk assessments, EPA concludes
that there is a reasonable certainty that
no harm will result to the general
population or to infants and children
from aggregate exposure to silver nitrate
V. Other Considerations
A. Analytical Enforcement Methodology
An analytical method is not required
for enforcement purposes since the
Agency is not establishing a numerical
tolerance for residue of silver nitrate in
or on any food commodities. EPA is
establishing a limitation on the amount
of silver nitrate that may be used in
pesticide formulations. That limitation
will be enforced through the pesticide
registration process under the Federal
Insecticide, Fungicide, and Rodenticide
Act (FIFRA), 7 U.S.C. 136 et seq. EPA
will not register any pesticide for sale or
distribution that contains greater than
0.06% of silver nitrate by weight in the
pesticide formulation.
B. International Residue Limits
In making its tolerance decisions, EPA
seeks to harmonize U.S. tolerances with
international standards whenever
possible, consistent with U.S. food
safety standards and agricultural
practices. EPA considers the
international maximum residue limits
(MRLs) established by the Codex
Alimentarius Commission (Codex), as
required by FFDCA section 408(b)(4).
The Codex Alimentarius is a joint U.N.
Food and Agriculture Organization/
World Health Organization food
standards program, and it is recognized
as an international food safety
standards-setting organization in trade
agreements to which the United States
is a party. EPA may establish a tolerance
that is different from a Codex MRL;
however, FFDCA section 408(b)(4)
requires that EPA explain the reasons

for departing from the Codex level.


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United States. Office of the Federal Register. Federal Register, Volume 75, Number 98, May 21, 2010, Pages 28463-28750, periodical, May 21, 2010; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc52679/m1/37/ocr/: accessed October 15, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.

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