Relationship between blood lead level and work related factors using the NIIH questionnaire system

Over an 11-yr period (1990-2000), a questionnaire survey on work environmental management and environmental improvement was conducted on 259 lead-handling factories and 7,623 subjects. Labour Inspection Offices identified these factories as requiring environmental improvement, or possessing a desire to improve their working environment. We analyzed factors affecting blood lead levels (PbBs). These factors were gender, age, employment duration, factory size, work environment control (WEC) class, and job categories. The PbB of men was found to be higher than that of women, and may be due to the differences in job distribution. PbB increased along with increasing age and employment duration. PbB declined as the factory size increased. The odds ratio (OR) of PbB higher than 20 microg/dl according to factory size was significantly high even after adjusting for WEC class. This demonstrates that not only the working environment but also safety management was poorer among small-scale factories that large-scale factories. The rise of PbB along with the increase of WEC class confirmed that the results of work environment measurement are correlated with individual exposure levels. The risk of having a 20 microg/dl or higher PbB was different for various lead handling jobs. Smelting or refining lead had the highest risk for lead exposure while painting or baking had the lowest risk. As our study population was not a randomly selected sample, we are unable to generalize our results for workers across Japan. However, we were able to indicate which jobs pose a high-risk and the effectiveness of using the work environment control class as an index of worksite environment levels.