are equivocal as to whether individuals with asthma respond at lower total exposures than healthy individuals, but the difference in threshold might be as high as 20-fold.

Data from SO2 and ozone do not show dramatic differences in sensitivity between individuals suffering from pre-existing lung diseases such as asthma or COPD and those without. Clinical studies with controlled SO2 exposure suggest that moderately to severely asthmatic individuals might show functional changes, on average, up to 20-fold more severe than those seen in controls but that asthmatic individuals begin to respond at a concentration no more than 5-fold lower than healthy individuals. For ozone, no similar data are available, and the few studies with people suffering from COPD have shown no differences either in the threshold or severity of response.

Data for all the inhalation toxicants discussed above, however, are for comparatively low exposure concentrations. Conceivably, at higher exposure concentrations, young children or individuals with compromised pulmonary or cardiovascular health might be more severely affected than healthy individuals. The subcommittee concludes that, in the general population, some individuals have pre-existing conditions that are likely to make them more sensitive to NO2, HCl, and HNO3 than healthy individuals both in the severity of response at a given exposure concentration and in the exposure concentration and duration required to initiate a response. Given that in the general population surrounding the launch sites, individuals are likely to be found who are more sensitive to the rocket-emission toxicants than healthy adults, the subcommittee believes that provisions should be made to ensure their protection. Where the data are equivocal, the subcommittee believes that the worst case possibility should be employed. Thus, the subcommittee recommends using the assumption that for short exposure durations (i.e., 1 hr or less), sensitive individuals begin to respond at lower concentrations than normal individuals by a factor of 10 for NO2, a factor of 3 for HCl, and a factor of 20 for HNO3.



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