Environmental Engineering Reference
In-Depth Information
TheInternationalAgencyforResearchonCancerhasclassiiedleadandinorganic
leadcompoundsinGroup2B:Possiblycarcinogenictohumans,andorganicleadin
Group3:Notclassiiable(IARC
1987
).
The carcinogenic potential of lead salts (primarily phosphates and acetates)
administeredviatheoralrouteorbyinjectionhasbeendemonstratedinratsand
mice by more than 10 investigators (Sanchez-Chardi et al.
2007
). The most char-
acteristiccancerresponseisbilateralrenalcarcinoma.Ratsgivenleadacetateor
subacetate orally developed gliomas disease, and lead subacetate also produced
lung adenomas in mice. Most of these investigations found a carcinogenic response
only at the highest dose. The lead compounds tested in animals are almost all
soluble salts. Studies of inhalation exposure have not been located in the
literature.
Missoun et al. (
2010
) conducted lab experiments on 14 male Wistar rats and
investigated the effects of lead acetate exposure on kidney function. The results
showed an increase in renal deficiency in lead exposed rats. Hamadouche et al.
(
2009
)investigatedreproductivetoxicityofleadacetateinadultratmales.Results
showed significant decrease in weight of sex glands and pituitary along with signifi-
cant reduction in sperm production.
There have been lot of controversy regarding the mathematical model for carci-
nogenic studies. The authors have chosen linear multistage model which is EPA's
model of choice for carcinogens. At low doses, the slope of the dose-response curve
is called potency factor (PF) or slope factor (SF) which is further used to calculate
lifetime incremental risk in the risk characterization section.
Risk Characterization
It is the final phase of risk assessment process where exposure and dose-
response studies are combined to yield probabilities of effects occurring in
humans under specific exposure conditions. Quantitative risk are calculated
using the default exposure parameters as discussed in exposure assessment
study and the slope factors or reference dose value obtained from dose-response
study. This integrated framework can be used by the risk managers to develop
guidelines for safety or for categorization of the study area on basis of accept-
ability of risk.
Cancer Risk
The model used is linear multi-stage model assuming dose-response curve to be
linear at low concentration of lead. The incremental lifetime risk of cancer can be
calculated using the following formulae:
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