Evaluation of a lead exposure reduction intervention for shutdown maintenance contractors at a primary lead smelter.

Abstract

Inorganic lead is a hazardous substance, exposure to which has been linked to various adverse health effects including haematological, neurological, renal and reproductive health problems. These adverse health effects can be correlated with blood lead levels (BLL) and are potentially significant for lead workers, such as production and maintenance personnel at lead smelters. Such workers usually need to wear particle-filtering respirators in order to reduce uptake of airborne lead, and follow strict hygiene protocols. However, there is a paucity of literature on the effectiveness of lead exposure reduction programs for lead smelter workers, especially those engaged as contractors for short periods. The aim of this study was to evaluate an intervention targeted at maintenance and refurbishment contractors engaged during a two-yearly plant shutdown of a primary lead smelter. This evaluation addressed a variety of factors that influence the uptake of lead and gathered information on a rarely-studied group of contractors so as to provide recommendations for improving future occupational health and safety (OHS) interventions in lead industries. Findings from the research may assist in refining conceptual models of OHS interventions addressing complex exposure scenarios. The intervention for the contractors entailed training and the mandatory use of a single brand of half-face disposable particle respirator. Contractors were instructed by the smelter management to undergo a pre-employment blood lead test and attend a health and safety induction, where they were informed of lead hazards and trained in the correct usage of disposable respirators. A post-induction questionnaire was used to elicit information on personal characteristics, smoking status, lead-based hobbies (hobbies that expose contractors to inorganic lead), prior respirator experience and perceptions of the use of disposable respirators. Fixed-position air sampling was conducted to determine the levels of airborne lead-bearing dust generated during maintenance activities and to assess differences between areas, including rest areas. Compliance with respirator usage requirements was assessed by routine observation, and site inspection checklists were used for the assessment of lead contamination. After the two-week shutdown period and prior to departure from the site, contractors underwent a second blood lead test. Other information was gathered prior to, during and after the intervention, through repeated observation and discussions with key stakeholders, and formed the basis of a stakeholder analysis. Full questionnaire and blood lead data were available for 62 male contractors, and of these 81% were previous contractors to the smelter, 87% had previous respirator experience, 78% believed disposable respirators were equal in protection to non-disposable rubber respirators, 87% were confident disposable respirators would keep blood lead down, and 35% reported non-occupational exposure to lead. The arithmetic mean entry BLL was 5.5 μg/dl (std dev=3.9) and the increase in BLL over the shutdown period was 14.4 (9.3). Smokers (n=18) had a mean increase of 17.4 μg/dl, compared to non-smokers (n=44) with 13.2 μg/dl, but this difference was not statistically significant. Similarly, potentially predictive factors such as age, job category, lead-based hobbies, respirator experience and confidence were not statistically significant. Crane operators and riggers (n=8) had the greatest increase in BLL (19.6), compared with welders (17.1, n=9) and general maintenance contractors (13.0, n=45). Although it was a non-smoking site, many contractors were observed to smoke. Observed compliance with respirator usage was generally good (estimated at 95% via direct observation). However it appeared that compliance and airborne lead dust levels were variable between locations, indicating these may be task related. Hot work, e.g. welding in confined areas, was associated with lower respirator usage and sweat-related respirator deterioration. Air monitoring in an area ostensibly lead-free, i.e. the blast furnace crib room (rest area), demonstrated appreciable levels of airborne lead dust (GM = 55 μg/m³, n=4). A stakeholder analysis of the intervention identified a lack of consultation between contractors and management prior to implementation. It was evident that smokers had difficulty complying with the strict non-smoking rules and that some contractors wore contaminated clothing in crib rooms, a source of lead exposure and a breach of policy. In addition, contractors were often unshaven, which significantly reduces the effectiveness of the mandated respirators. Finally, some contracting companies exhausted their supply of respirators, suggesting logistical problems and limited consultation. This study appears to be the first to report increases in blood lead for a cohort of shutdown maintenance contractors working in a lead smelter environment. It also demonstrates appreciable BLL increases in a relatively short space of time. The findings relating to airborne lead and to BLL differences between contracting companies indicate that lead uptake is associated with task and that the use of a half-face disposable respirator with moderate protection performance may not be suitable for all tasks. The lack of personal inhalational exposure data limits the interpretation of the effectiveness of the respiratory protection program based on BLL alone. The stakeholder analysis highlighted disparate management and contractor perspectives on consultation. Overall, however, the intervention was judged as successful by the lead smelting company on the basis of observed respirator compliance and by a crude comparison with BLL data observed in a previous shutdown period, two years earlier. It is recommended that task-specific personal air sampling be undertaken, especially for hot work, in order to determine whether the half-face respirator is adequate for all tasks. The induction training should more explicitly address routes of lead exposure and the importance of factors determining respirator effectiveness. A greater degree of consultation between contracting companies and smelter management should be undertaken in order to address logistics issues, work practices and hygiene, especially for smokers. This study has highlighted the complexity of exposure pathways, often mediated by worker behaviour in response to company directives, and relatedly, the value of stakeholder analysis as a means of identifying areas for improvement. The change in BLL serves as an index of actual success for future interventions.