Get full text report(pdf file; Read by ADOBE Acrobat Reader)
J Occup Health year 2002 volume 44 number 5 page 355 - 359
Classification Original
Title An Approach to Evaluating Occupational and Environmental Regulatory Standards:
With a Drinking Water Standard for Arsenic as an Example
Author How-Ran GUO
Organization Graduate Institute of Environmental and Occupational Health, Medical College, National Cheng Kung University, Taiwan
Keywords Regulatory standard, Arsenic, Risk assessment, Skin cancer, Meta-analysis, Validation study
Correspondence H.-R. Guo, Graduate Institute of Environmental and Occupational Health, Medical College, National Cheng Kung University, 138 Sheng-Li Road, Tainan 70428, Taiwan
Abstract An Approach to Evaluating Occupational and Environmental Regulatory Standards: With a Drinking Water Standard for Arsenic as an Example: How-Ran GUO. Graduate Institute of Environmental and Occupational Health, Medical College, National Cheng Kung University, Taiwan -Occupational and environmental regulatory standards are usually determined on the basis of data from high-dose exposures, either in humans or animals. Risk assessment models are applied to identify the level below which the risks are considered as acceptable. Even when the basis is human data, the validity of extrapolation is often questionable because the number of cases actually observed in the low-dose region is usually small, if any. Validation of the risk assessment model by using data on populations with low-dose exposures is desirable, but the lack of study power is the major concern in most cases. A meta-analysis combining data from more than one study may solve the problem, especially when a model overestimates risks associated with low-dose exposures. A maximum contaminant level (MCL) of arsenic in drinking water at 0.05 mg/l published by the US Environmental Protection Agency (EPA) was used as an example to demonstrate such a scenario. Because this MCL was derived by using data from a study on skin cancer in Taiwan, a validation was conducted by using data on Taiwanese with low-dose exposures. In comparison with the number of cases observed in four studies, the model was more likely to be invalid than to be valid at exposure levels below 0.17 ppm and overestimated the number of cases (11.08 vs. 5). Whereas the EPA has published a new MCL recently on the basis of new risk assessments on urinary bladder and lung cancers, re-visiting the validity of the old standard still provides insights for validating regulatory standards in the future.