Mortality and Occupational Lead Exposure by Industry Type: An Analysis of a UK Lead-Exposed Cohort with Blood Lead Levels, 1975-2011 Open Access

Liu, Jennifer (2017)

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BACKGROUND: In 2006, the International Agency for Research on Cancer (IARC) concluded that inorganic lead is probably carcinogenic. Since then, only a few occupational worker cohorts have further examined the association between inorganic lead exposure and cancer mortality. Worker cohorts represent a unique sector of exposed individuals that can be used to assess documented lead exposure and associations with disease outcomes of interest.

OBJECTIVE: We examined the mortality of a historic cohort of workers in Great Britain using industry-defined blood lead levels (BLLs), whereby mean BLLs in an industry were assigned to all workers in that industry. We compared our results to those of McElvenny et al. (2015), which is currently the only paper published on this cohort. McElvenny et al. conducted analyses by industry categories defined by expert opinion, as well as by individual maximum BLL.

METHODS: We analyzed associations between occupational lead exposure and all-cause/cause-specific mortality among 9122 workers with measured blood lead levels from 1975 to 1979, and follow-up through 2011. Along with descriptive statistics, trends in mortality using industry-defined lead exposure and individual maximum BLLs were examined using Cox regression.

RESULTS: Mean follow-up length among the 9122 study participants was 29.2 years and 3480 deaths occurred. No consistent positive trends were found for any cause of death using industry-defined exposure. For trend tests conducted using individual maximum BLL, there were significant positive trends between increasing lead exposure and all-cause mortality (p=<0.0001), chronic obstructive pulmonary disease (p=0.02), cerebrovascular disease (p=0.04), and ischemic heart disease (p=0.03), which were generally concordant with the trend test results from McElvenny et al. which also used individual maximum BLL.

CONCLUSION: Our results were concordant with McElvenny et al. in that we found no monotonic trends using an industry-wide assignment, but we did find positive trends for lead exposure based on individual maximum BLL in all-cause mortality, chronic obstructive pulmonary disease, stroke, and ischemic heart disease. Therefore, using individual maximum BLL may be a better metric of assessing lead exposure in this cohort rather than using an industry-focused analysis. Further work is required to clarify the resulting associations and the carcinogenicity of lead.

Table of Contents

Introduction 1

Background 1

Goals of Present Study 3

Methods 6

Study Design & Population 6

Analysis 8

Results 10

Discussion 14

Limitations 16

Conclusion 18

References 19

Tables 21

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