Exposure estimates daily rate

The time period to use in estimating and grouping pollutant intake values is determined by the eventual application of the exposure results. Exposure medium intake rates may vary on a daily (e.g., for inhalation) or seasonal (e.g., for recreational dermal absorption) basis. If the variability has a significant influence... 

The report estimated a lifetime risk of excess bone sarcomas per million people of 1.5 if soluble uranium isotopes were ingested at a constant daily rate of 1 pCi/day (0.037 Bq/day). The number of bone sarcomas that occur naturally in a population of a million people is 750. However, no quantitative risk coefficient estimates for developing human exposure protection benchmarks were provided in this report. In addition, the BEIR IV analysis was presumably based on generic short-lived alpha-emitting sources, such as radon that have a higher potential for inducing cancer, and not on radionuclides with relatively longer radioactive half-lives like and Perhaps more importantly, the BEIR IV report... 

The general population can be exposed to chemical substances in indoor as well as in outdoor (ambient) air via inhalation of vapors, aerosols, and dusts in the air. The term inhalation exposure is defined as the concentration of a substance in inhaled air at the boundary of the body, and is expressed as an average concentration per unit time (e.g., mg/m per day). In order to estimate a daily dose of a substance from the exposure concentration of the substance in the air, the inhalation rate is used. According to US-EPA (1997), the average daily dose (ADD) can be estimated from the exposure concentration by using the following equation ... 

In summary, conversion of biomonitoring data to exposure dose requires knowledge of chemical elimination rate and Vd and requires that conditions be approximately pseudosteady state. It may be useful to estimate dose from body burden however, this cannot be used to interpret an individual s biomonitoring result, because the elimination rate and Vd would not be known. Reasonable bounds on elimination rate and Vd could be used to calculate an upper end of daily dose that is still compatible with the biomonitoring results (for example, when both Vd and elimination rate are high). 

Exposure factors The inputs used to translate unit exposure values (p-g/kg a.i. handled) to estimates of an individual s daily exposure (pg/kg b.wt./d), which can then be compared to no effect levels in mammalian toxicology studies or acceptable operator exposure levels (AOELs). Exposure factors can be categorized as (i) physiological (inhalation rates, body weights and lifespan), (ii) pesticide usage (dmation of activity, acreage Peated per day, etc.) and (iii) lifestyle (activity patterns and co-occurrence information) (Norman, Ch. 10). 

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