Low-Level Lead Exposure Among South Korean Lead Workers, and Estimates of Associated Risk of Cardiovascular Diseases

Abstract

This study investigated the distribution of blood lead (PbB) levels, especially low levels, among Korean lead workers. The authors also estimated the potential effects of PbB on the blood pressure (BP) and cardiovascular diseases using models taken from the published meta-analyses. The PbB data from a total of 13,043 lead workers in 1217 companies throughout Korea were used. The geometric mean PbB level was 6.08 μ g/dL (geometric standard deviation was 2.53), and 56.6% of the workers showed PbB levels greater than 5 μ g/dL. Females accounted for 31.3% of all Korean lead workers in 2003. Considering two factors, such as PbB levels and the number of lead workers, the relatively important industry subclasses were identified as Manufacture of Accumulators; Manufacture of Other Electronic Valves, Tubes, Electronic Components n.e.c.; and Manufacture of Other Parts and Accessories for Motor Vehicles. The industrial processes of relative importance included battery assembly, acid treatment, and other soldering. Although uncertainties exist in the prediction model and associated model parameters, the authors attempted to estimate potential adverse health effects related to the lead exposure. It was estimated that 7383 South Korean lead workers might have increased blood pressure and the health risks due to the lead exposures in 2003. The highest estimated risk of BP increases due to lead exposures was expected in workers of industrial subclasses and processes, such as Other Basic Nonferrous Metal Industries and Maintenance. If the models in this study were applied to the South Korean population, the impact fractions for cardiac disease among lead workers would be estimated at 4.9–12.8 times those of the general population.

Keywords:

• blood lead level
• blood pressure
• cardiovascular disease
• disease burden
• low-level lead exposure
• South Korean lead workers

ACKNOWLEDGMENTS

The authors thank Mr. Sungwon Choi and his team members from KOSHA, and Mr. Jeongin Lee from KMOL for permission to use the raw data from the 2003 Special Health Surveillance. The authors are grateful to Doug Parker from 3M for his thorough review and comments that improved the presentation of this article.

Notes

^A These data do not include general population for any PbB categories.

^B Employment durations were different for PbB ranges (ANOVA test: p < 0.001).

^C Male workers have longer employment duration than female workers at a designated PbB range category (two-sample t-test: P < 0.05).

^D Male workers have higher PbB concentration than female workers at a designated PbB range category (two-sample t-test: p < 0.001).

^A Weighted average value of relative risk for 15- to 59-year-old males.

^B Weighted average value of relative risk for 15- to 59-year-old females.

^C Ischemic heart disease.

^D Cerebrovascular disease.

^A Other dry means drying other than hot air dry.

^B Other soldering means soldering other than iron soldering, dipping soldering, silver soldering, and automatic soldering.

^C Other welding means welding other than arc welding, CO₂ arc welding, plasma arc welding, MIG welding, TIG welding, gas welding, electron beam welding, electric welding, spot welding, submerged welding.

^D Other melting means melting process other than aluminum melting, lead melting, and alloy melting.

^A Estimated blood pressure increase of male due to lead exposure.

^B Estimated relative risk of ischemic heart disease of male due to increased blood pressure.

^C Estimated relative risk of cerebrovascular disease of male due to increased blood pressure.

^D Estimated relative risk of hypertensive disease of male due to increased blood pressure.

^E Estimated relative risk of other cardiac disease of male due to increased blood pressure.

^F Estimated blood pressure increase of female due to lead exposure.

^G Estimated relative risk of ischemic heart disease of female due to increased blood pressure.

^H Estimated relative risk of cerebrovascular disease of female due to increased blood pressure.

^I Estimated relative risk of hypertensive disease of female due to increased blood pressure.

^J Estimated relative risk of other cardiac disease of female due to increased blood pressure.

^A Estimated blood pressure increase of male due to lead exposure.

^B Estimated relative risk of ischemic heart disease of male due to increased blood pressure.

^C Estimated relative risk of cerebrovascular disease of male due to increased blood pressure.

^D Estimated relative risk of hypertensive disease of male due to increased blood pressure.

^E Estimated relative risk of other cardiac disease of male due to increased blood pressure.

^F Estimated blood pressure increase of female due to lead exposure.

^G Estimated relative risk of ischemic heart disease of female due to increased blood pressure.

^H Estimated relative risk of cerebrovascular disease of female due to increased blood pressure.

^I Estimated relative risk of hypertensive disease of female due to increased blood pressure.

^J Estimated relative risk of other cardiac disease of female due to increased blood pressure.

^A Accumulator; Manufacture of Accumulators, Electronic Components; Manufacture of Other Electronic Valves, Tubes, and Electronic Components n.e.c., Motor Part; Manufacture of Other Parts and Accessories for Motor Vehicles, Nonferrous Metal, Other Basic Nonferrous Metal Industries, Wireless Communications; Manufacture of Communication Apparatuses Without Any Line Connection and Radio or Television Broadcasting Apparatuses.

^B Source of PbB level is Reference 15.

^C The impact fraction is the percentage of the population risk that can be attributed to lead exposure. To calculate the fraction of disease attributable to lead exposure for South Korean lead workers, the total disease burden for the South Korean lead workers (in deaths and DALYs) caused by the selected cardiac diseases is multiplied by the impact fraction.

^A Regression equation was derived from a defined BP increase rate and age-weighted relative risks for cardiovascular diseases as presented in Figure 2. Age-weighted relative risks were derived from the comparative risks reported by Lawes et al.^{( 14 )} and age distribution of study population using Eq. 1.

^B y is the estimated relative risk of a cardiovascular disease of South Korean lead workers.

^C x is the estimated BP increase.