Studies on the Modifications of Some Screening Methods for Health Examination in Lead Workers

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The determinations of urinary <delta> -aminolevulinic acid (ALA), urinary coproporphyrin (COPRO) and blood lead are useful in evaluating the health effect by lead in workers occupationally exposed to lead. The present study was undertaken to simplify some screening methods being utilized for checking the health effect in lead workers. The results were as follows:1. Determination of urinary ALA; We modified an original method of Tomokuni and Ogata. When urinary ALA was determined using the original method of Tomokuni and Ogata after 3-fold dilution of urine with distilled water, it was possible to eliminate the urinary matrix interference. As for the condensation reagent for ALA-pyrrole, methyl acetoacetate was superior to ethyl acetoacetate.2. Determination of urinary COPRO; The conventional methods (Rimington method and its modification) based on sample extraction and the spectrophotometric measurement at the peak of the Soret band for COPRO are very time-consuming. In the present study, we developed a simplified method for determining urinary COPRO in lead workers, using a high-performance liquid chromatograph (HPLC) equipped with a fluorescence detector. The detection limit of urinary COPRO in this method was 5 ug per liter of urine. The working linear range of urinary COPRO concentration was 5 to 1500 ug/L. This HPLC method is simpler and more rapid than the spectrophotometric method and is useful in mass screening for lead exposure.3. Determination of blood lead; We modified a method of Hodges and Skelding for determining blood lead by flameless atomic absorption spectrophotometry. In the present method, a graphite tube was coated with molybdenum and both Triton X-100 and phosphoric acid were added to whole blood. The calibration curve was made by adding standard lead solution to the pooled blood of normal controls. This method was more reliable compared to the original method.