Air Quality Criteria for Lead Volume II of II - (NEPIS)(EPA) - US ...

1994. mSQGQs are useful to risk assessors but their inherent limitations and underlying
assumptions must be fully understood (see Section AX7.2.1.5).
Summary of Interactions With Other Pollutants
Norwood et al. (2003) reported that in a review and reinterpretation of published data on
the interactions of metals in binary mixtures (n = 15 studies), antagonistic (6) and additive
interactions (6) were the most common for Pb. The complexity of the interactions and possible
modifying factors makes determining the impact of even binary metal mixtures to aquatic biota
difficult (Norwood et al., 2003; Playle, 2004). The two most commonly reported Pb-element
interactions are between Pb and calcium and between Pb and zinc. Both calcium and zinc are
essential elements in organisms and the interaction of Pb with these ions can lead to adverse
effects both by increased Pb uptake and by a decrease in Ca and Zn required for normal
metabolic functions.
AX7.2.3.5 Factors Associated with Global Climate Change
It is highly unlikely that Pb has any influence on generation of ground-level ozone,
depletion of stratospheric ozone, global warming, or other indicators of global climate change.
Lead compounds have relatively short residence times in the atmosphere, making it unlikely that
they will reach the stratosphere, and they do not absorb infrared radiation, making them unlikely
to contribute to stratospheric ozone depletion or global warming. Also, these compounds are
unlikely to have a significant interaction with ground-level nitrogen oxides or volatile organic
compounds, thus precluding generation of ground-level ozone.
Approached from another viewpoint, climate change can have a major impact on the
fate/behavior of Pb in the environment and, therefore, can subsequently alter organism or
ecosystem responses. For example, changes in temperature regime (Q10 rule), changes in
precipitation quantity and quality (e.g., acidic deposition) may influence fate, transport, uptake,
and bioavailability of Pb (Syracuse Research Corporation., 1999).
AX7.2.3.6 Summary
There have been a number of advancements in the understanding of Pb behavior in the
environment and its impact on aquatic organisms since 1986. In particular, greater knowledge of
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