PRINCIPLES OF TOXICOLOGY

19.6 REEVALUATION OF THE CARCINOGENIC RISKS OF INHALED ANTIMONY TRIOXIDE 495
sponse data available from these studies. Further reducing the weight-of-evidence for a carcinogenic
effect of inhaled antimony trioxide in humans is the fact that positive results have only been obtained
from a single species (rat), single site (lung), and a single sex (females).
Other data may also be considered in weight-of-evidence determinations. Genotoxicity is an
important component in determining weight of evidence for the potential carcinogenicity of a chemical.
In the case of antimony trioxide, genotoxicity test results are mixed. This data is inconclusive regarding
the potential for antimony trioxide to cause genetic damage in humans.
TABLE 19.10 Air and Soil Exposure Equations
Air
Inhalation of vapor-phase or particulate-phase chemicals in air:
CA × VR × EF × ED
Daily intake in mg/kg =
BW × AT
where CA = modeled or actual concentration of chemical in air (mg/m 3 )
VR = inhalation rate (m 3 /day or event)
EF = exposure frequency (days/year)
ED = exposure duration (years)
BW = body weight (kg)
AT = averaging time [period over which exposure is averaged (ATnc for noncarcinogens:
ED × 365 days/year; ATc for carcinogens: 70 years × 365 days/year)]
Soil
Ingestion of chemicals in soil:
CS × IR × ABSgi × EF × ED × CF
Daily intake in mg/kg =
BW × AT
where CS = chemical concentration in soil (mg/kg)
IR = ingestion rate (mg soil/day)
ABSgi = fraction of chemical absorbed from soil relative to fraction absorbed from food or water
EF = ingestion exposure frequency (days/year)
ED = exposure duration (years)
CF = conversion factor (1 × 10 –6 kg/mg)
BW = body weight (kg)
AT = averaging time [period over which exposure is averaged (ATnc for noncarcinogens: ED × 365
days/year; ATc for carcinogens: 70 years × 365 days/year)]
Dermal absorption of chemicals in soil:
CS × SA × AF × ABSsk × EF × ED × CF
Absorbed dose in mg/kg/day =
BW × AT
where CS = chemical concentration in soil (mg/kg)
SA = skin surface area availab le for contact (cm 2 )
AF = adherence of soil to skin (mg/cm 2 )
ABSsk = fraction of chemical absorbed though the skin
EF = exposure frequency (days/year)
ED = exposure duration (years)
CF = conversion factor (1 × 10 –6 kg/mg)
BW = body weight (kg)
AT = averaging time [period over which exposure is averaged (ATnc for noncarcinogens: ED × 365
days/year; ATc for carcinogens: 70 years × 365 days/year)]