[Dose-response relationships at different exposure levels. Re-examination in establishing no-effect levels (author's...

In this study dose-response and dose-effect relationships were examined with reference to no-effect levels using observed data from three groups of lead workers who had been exposed to three different concentrations of lead. Blood lead concentration (PbB) was used for "dose" and ALA concentration in urine (ALAU) and rate for 5 mg/l or greater of ALAU were used as "effect" and "response" respectively. Dose-effect and dose-response relationships between PbB and ALAU of these three different exposure populations indicated three different curves although theoretically they should all have indicated a similar curve. This means that "effect" or "response" for the highest exposure group was higher than that for the lowest exposure group on the same "dose" level. This difference is statistically explained for the most part by variations in the determinations of "dose" (PbB) as well as "effect" or "response" (ALAU). In view of the above results, it would seem that re-examination is required in establishing criteria of no-effect levels for dose-response relationships of various environmental chemicals.