Benchmark Dose Of Occupational Lead Exposure

Lead, a widely-used material in industry, is seriously harmful tooccupational population. Lead persistent affects human health due to itslong-term existence in the environment resulting from its undecomposablenature. Following the industry production techniques, the innovation ofoperation process and the improvement of occupational and environmentalprotection, the acute lead poisoning with obvious clinical signs andsymptoms has been largely controlled. However, the serious concern hasbeen increasingly paid to the insidious effect due to low level and longterm lead exposure. The purposes of the present study are to explore dose-response relationshipsbetween lead and nervous system, blood system and renal dysfunction using themethod of epidemiological investigation and the relationship betweenδ-aminolevulinic acid dehydratase (ALAD) gene polymorphism and lead toxicity,and estimate benchmark dose (BMD) , the lower confidence limit of the benchmarkdose (BMDL) and the biological exposure limits(BEL) for the adverse effects ofrenal, nervous and blood systems. In addition, the variation for BMD of blood lead indifferent ALAD genotypes was also investigated. Part 1 Occupational lead exposure 135 workers from a storage battery plant were selected as lead exposure groupwhile 143 mechanics and students as the control group. Two groups are comparable inage, sex, education level, smoking and drinking habits. Systematical environmentmonitoring was performed on workplaces of the plant in order to assess the leadpollution. The geometric means were 0.15mg/m3 and 0.05 mg/m3, and the exceedingrates(the percentage of air lead level above MAC)were 69.8% and 76.8%, for air leaddust and lead fume, respectively. The average level of blood lead was 42.15μg/dl inlead exposed group, which was remarkably higher than that of the control group. Part 2 Effect of lead on neurobehavior Neurobehavioral test is commonly recognized as a sensitive and simple test fordetecting early dysfunction of central nervous system associated with exposure to 4neuro-toxic agents, such as heavy metals. In this study, we attempted to applyNeurobehavior Cores Test Battery (NCTB) (recommended by WHO) includingprofile of mood states (POMS) and 6 items of neurobehavioral tests to investigatelead-induced neurobehavioral impairment. The results of the test indicated that: thescores of mood states, digital span(DSP)and pursuit aiming(PA) in low leadexposure workers (blood lead < 40μg/dl or employment duration < 5 years)changed significantly; the changes of digit symbol(DSY), Benton visual retention(BVR) and Santa Ana(SAN) also occurred in high lead exposure workers(blood lead≥40μg/dl or employment duration≥5 years). The factor analysisshowed that lead exposure affected negative and positive mood factor, memory factorand motor coordination factor. There was a significant correlation between blood leadlevel and negative mood factor, positive mood factor and memory factor. Results ofthe multiple linear stepwise regression analysis were similar to the findings above. Using discriminant analysis, it had been showed that depression-dejection(POMSD), vigor-activity(POMSV), fastest simple reaction(SRTF), dignity spanbackward(DSPB), correct dot number(PAC)and error dot number(PAE)ofWHO/NCTB seemed to be the key sub-tests for detecting the neuropsychologicaleffects of lead exposure. Part 3 Effects of lead on metabolism of porphyrin and renal function It is well known that lead affects the metabolism of porphyrin. This studyshowed that the urinary δ-aminolevulinic acid (ALA) increased with elevated bloodlead level in lead exposure workers. The level of urinary ALA in low lead exposuregroup (<5 years of employment) was higher than that of the control group.Moreover, there was a significant positive correlation between urinary ALA and bloodlead. The urinary enzymes and low-molecular we...