Receptors toxic gases

First, we analyzed samples for a large number of elements to Identify any elements, regardless of toxicity or typical concentration, that would provide signals for the presence of material from certain types of sources. Both ambient samples and particles from sources were analyzed by Instrumental neutron activation analysis (INAA), by which one can often measure about 35 elements In Individual samples (17), As the Important elements Pb, N1 and Cd are not consistently, If ever, observed by INAA, they were often measured by other methods. As INAA Is sensitive to very small amounts of obscure elements, we have obtained reliable data for elements such as Ga, Hf, Sc, In, W and many rare earths which pose no known health hazard at present levels and contribute Insignificant amounts of mass to TSP. However, as discussed below, many trace elements have already been shown to be Important In receptor... 

The chemical concentrations identified in the data evaluation component are combined with all of these exposure or intake assumptions into equations to estimate a dose in units of milligrams chemical per kilogram body weight per day. These are the same units in which toxicity data are reported, as discussed in chapter 7. For the gas station example, the results of this step would include chemical-specific dose estimates for all complete exposure pathways for each receptor. These dose estimates are combined with the toxicity values discussed below in the risk characterization component of a risk assessment. 

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