A cohort study on blood zinc protoporphyrin concentration of workers in storage battery factory

Jeon, Man Joong; Lee, Joong Jeong; Sakong, Joon; Kim, Chang Yoon; Kim, Jung Man; Chung, Jong Hak

Abstract

To investigate the effectiveness of the interventions in working environment and personal hygiene for the occupational exposure to the lead, the blood zinc protoporphyrin(ZPP) concentrations of 131 workers ( 100 exposed subjects and 31 controls ) of a newly established battery factory were analyzed. They were measured in every 3 months up to 18 months. Air lead concentration (Pb-A) of the workplaces was also checked for 3 times in 6 months interval from August 1987. Environmental intervention included the local exhaust ventilation and vacuum cleaning of the floor. Intervention of the personal hygiene included the daily change of clothes, compulsory shower after work and hand washing before meal, prohibition of cigarette smoking and food consumption at the work site and wearing mask. Mean blood ZPP concentration of the controls was 16.45+/-4.83 microgram/dashliter at the preemployment examination and slightly increased to 17.77+/-5.59 microgram/dashliter after 6 months. Mean blood ZPP concentration of the exposed subjects who were employed before the factory was in operation (Group A) was 17.36+/-5.20 microgram/dashliter on employment and it was increased to 23.00+/-13.06 microgram/dashliter after 3 months. The blood ZPP concentration was increased to 27.25+/-6.40 microgram/dashliter on 6 months (p<0.01) after the employment which was 1 month after the initiation of intervention program. It did not increase thereafter and ranged between 25.48 microgram/dashliter and 26.61 microgram/dashliter in the subsequent 4 results. Mean blood ZPP concentration of the exposed subjects who were employed after the factory had been in operation but before the intervention program was initiated (Group B) was 14.34+/-6.10 microgram/dashliter on employment and it was increased to 28.97+/-7.14 microgram/dashliter (p<0.01) in 3 months later(1 month after the intervention). The values of subsequent 4 tests were maintained between 26.96 microgram/dashliter and 27.96 microgram/dashliter. Mean blood ZPP concentration of the exposed subjects who were employed after intervention program had been started (Group C) was 21.34+/-5.25 microgram/dashliter on employment and it was gradually increased to 23.37+/-3.86 microgram/dashliter (p<0.01) after 3 months, 23.93+/-3.64 microgram/dashliter after 6 months, 25.50+/-3.01 microgram/dashliter (p<0.01) after 9 months, and 25.50+/-3.10 microgram/dashliter after 12 months. Workplaces were classified into 4 parts according to Pb-A. The Pb-A of part I, the highest areas, were 0.365 microgram/m4, and after the intervention the levels were decreased to 0.216 microgram/m4 and 0.208 microgram/m4 in follow-up test. The Pb-A of part II which was resulted in lower value than part I was decreased from 0.232 microgram/m4 to 0.148 microgram/m4, and 0.120 microgram/m4 after the intervention. The Pb-A of part III was tested after the intervention and resulted in 0.124 microgram/m4 in January 1988 and 0.081 microgram/m4 in August 1988. The Pb-A of part IV was also tested after the intervention and resulted in 0.110 microgram/m4 in August 1988. There was no consistent relationship between Pb-A and blood ZPP concentration. The blood ZPP concentration of the group A and B workers in the part of the highest Pb-A were lower than those of the workers in the parts of lower Pb-A. The blood ZPP concentration of the workers in the part of the lowest Pb-A increased more rapidly. The blood ZPP concentration of the group C workers was the highest in part III. These findings suggest that the intervention in personal hygiene is more effective than environmental intervention, and it should be carried out from the first day of employment and to both the exposed subjects, blue color workers and the controls, white color workers.