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

AX7.1.3.3 Recent Studies on the Effects of Lead on Consumers
Since the 1986 Lead AQCD (U.S. Environmental Protection Agency, 1986a), there have
been several studies in which birds and mammals were exposed to Pb via ingestion (primarily
through dietary Pb). Many of these were reviewed during development of the Eco-SSLs (U.S.
Environmental Protection Agency, 2005b). The relevant information from the Eco-SSL
document (U.S. Environmental Protection Agency, 2005b) is described below. A literature
search and review was conducted to identify critical papers published since 2002. These recent
critical papers are described briefly below. No studies were found that used inhalation exposures
to evaluate endpoints such as survival, growth, and reproduction in birds or mammals. All
studies described below exposed organisms via ingestion (drinking water or diet) or gavage.
The Eco-SSLs for avian and mammalian consumers are presented as Pb concentrations in
soil. These concentrations were calculated by assuming exposure to Pb via incidental soil
ingestion and ingestion of Pb-contaminated food, and using a NOAEL as the TRV (U.S.
Environmental Protection Agency, 2005a). A simplified version of the equation used to
calculate the Eco-SSL is:
HQ=
[ ( C soil × IRsoil)
+ ( Cfood×
IRfood)
]
AX7-64
TRV
where:
HQ = hazard quotient (1 mg Pb/kg bw/day)
Csoil = concentration of Pb in soil (mg Pb/kg soil)
IRsoil = incidental soil ingestion rate (kg soil/day)
Cfood = concentration of Pb in food (mg Pb/kg food)
IRfood = food ingestion rate (kg food/day)
BW = body weight (kg)
TRV = toxicity reference value (mg Pb/kg bw/day)
÷ BW
Food ingestion was estimated by modeling the uptake of Pb from soil into each diet
component (e.g., vegetation, invertebrates, etc.). Bioavailability of Pb in soil and food was
assumed to be 100%. The Eco-SSL is equivalent to the concentration of Pb in soil that results in
an HQ = 1. The two factors that may have the most significant influence on the resulting Eco-
SSL are the assumption of 100% bioavailability of Pb in soil and diet and the selection of the
(AX7-4)