Abstract
Objective:
Take-home lead exposure involves lead dust inadvertently carried from the worksite by employees that becomes deposited in their homes and vehicles. We piloted a program in 2 counties in Michigan to investigate the countywide potential for take-home lead exposures across industries.
Methods:
During 2018-2020, we identified establishments through internet searches and industry-specific registries. We visited establishments with a physical storefront in-person; we attempted to contact the remaining establishments via telephone. We administered questionnaires at the establishment level to assess the presence of lead and the current use of practices meant to mitigate the potential for take-home lead exposures. We recruited workers for wipe sampling of lead dust from their vehicle floors to test for lead levels.
Results:
We identified 320 establishments with potential lead use or exposures. Questionnaire responses revealed widespread worker exposures to lead and a lack of education and implementation of best practices to prevent lead from leaving the worksite. Dust samples (n = 60) collected from employee vehicles showed a ubiquitous tracking of lead out of the workplace, with a range of 5.7 to 84 000 µg/ft2 and a geometric mean of 234 µg/ft2. Of the sample results, 95.0% were above the lead dust clearance levels for homes established by the US Environmental Protection Agency.
Conclusions:
This work suggests that take-home lead exposures are widespread and may be important sources of lead exposure among children. It also demonstrates the feasibility of a program for the identification of establishments whose employees may be susceptible to taking lead dust home with them and whose children may subsequently be targeted for blood lead monitoring.
Children of parents whose occupations involve exposures to lead are vulnerable to take-home exposures from lead inadvertently carried off the worksite by the parent on their skin, clothes, or shoes, and deposited in their homes or vehicles. Previous investigations identified high lead loading of dust in the homes or vehicles of workers in the construction 1 and lead-based paint remediation 2 industries. Other studies found elevated blood lead levels in the children of construction, 3 radiator repair,4,5 battery repair and recycling,6,7 scrap metal recycling,8,9 painting and paint removal, 9 furniture repair, 10 and lead oxide manufacturing 11 workers. One meta-analysis found that 52% of children of lead-exposed workers had blood lead levels >10 µg/dL, compared with 8.9% of children in the general US population. 12 The Centers for Disease Control and Prevention considers blood lead levels ≥5 µg/dL to be elevated in both children and adults.13,14 Wipe sampling for lead dust suggests exposures may occur even in nonproduction areas of workplaces, as well as in firing ranges and gun stores. 15
The Michigan Adult Blood Lead Epidemiology and Surveillance (ABLES) program found a higher prevalence of blood lead levels ≥10 µg/dL among children of lead-exposed workers in Michigan than among all children screened in the state. 16 During 1997-2016, only one-third of children aged ≤6 years whose parent had a blood lead level ≥10 µg/dL from an occupational exposure had a blood lead test. 16 Among the children who were tested, 35% had a blood lead level ≥10 µg/dL. 16 This prevalence is much higher than the 3.6% prevalence of elevated blood lead levels ≥5 µg/dL reported across all children screened in Michigan. 17
To investigate whether the high prevalence of elevated blood lead levels in people who work with lead and their children in turn reflects the occurrence of potential take-home exposures, we designed and implemented a pilot program for evaluation of the potential for take-home lead exposure in 2 Michigan counties, Genesee and Ingham. Our objective was to evaluate whether lead dust was leaving the workplace with workers, as represented by the presence of lead dust in their personal vehicles, and identify which workplace policies and practices might be targeted for future exposure mitigation. We used the results of this study to develop a guidance document that state and local health departments can use to conduct evaluations of take-home lead for the prioritization of children for lead poisoning interventions. 18
Methods
A detailed explanation of the methods used in this project can be found in the guidance document developed for health departments during this project. 18 The Michigan State University Institutional Review Board reviewed the protocol and exempted it as a public health activity.
Establishment Identification and Contact
During 2018-2020 (October 1, 2018–September 30, 2019, for Genesee County; October 1, 2019–September 30, 2020, for Ingham County), we identified establishments via internet searches for businesses in Genesee and Ingham counties in industries known to involve the use of, and worker exposure to, lead. These industries were selected from those identified in Michigan with workers with elevated blood lead levels 16 and a literature review. Industries included automobile repair shops (particularly establishments that focused on radiator repair), firing ranges, establishments that produced and/or applied industrial paints and coatings, lead acid battery collection and recycling centers, and scrap metal collection, recycling, and resale establishments. We also accessed the State of Michigan list of certified contractors and individual workers performing lead paint remediation and/or inspection. 19 We identified demolition contractors working in Genesee County through public records maintained by the Genesee County Land Bank. We defined an “establishment” as a single business or a single location of a chain business. For the lead paint abatement and demolition industries, we defined contractors as “establishments” regardless of the number of ongoing worksites.
A trained environmental sanitarian contacted each establishment via an in-person visit when possible and a telephone call otherwise (eg, for establishments without a physical storefront). At each establishment, we asked 1 employee to complete a questionnaire reflecting the establishment-wide use of work practices and policies that would mitigate the amount of lead dust leaving the workplace. We adapted the list of practices on the questionnaire from previous studies of take-home lead. 1 We provided all establishments that were successfully contacted with educational materials (either in-person during a visit or through mail) developed by the Michigan Department of Health and Human Services20,21 and the North Carolina Department of Health and Human Services22,23 on take-home lead exposure and the cleaning of lead dust, along with resources for obtaining blood lead testing.
Dust Wipe Sampling
During contact with the establishment, we took dust samples from the personal vehicles of all employees who were at the workplace during the visit and were willing to participate. We collected samples from more than 1 employee at an establishment if multiple employees volunteered. We did not collect information on the total number of workers at an establishment, so we could not calculate the participation rate among workers. We used GhostWipes (Environmental Express) per a protocol used by the Michigan Department of Health and Human Services to perform dust sampling. 24 We placed a disposable 100-cm2 template on the driver-side vehicle floor mat or floorboard. We collected dust on the template by using 3 consecutive wiping patterns. We collected samples on the superficial surface of the driver’s seat floor, including carpeted floor mats if present. Wipe samples are an efficient means of collecting lead dust on carpeted surfaces; although wipes may not collect dust from deep in the carpet, the surface lead dust they do collect correlates with child blood lead levels.25-27 For quality control, we collected and analyzed 1 field blank (a new, unused wipe used to determine whether any systematic lead contamination is present in the handling of the samples during collection and analysis) for each day of establishment visits. The Michigan Occupational Safety and Health Administration (OSHA) laboratory analyzed samples for lead using inductively coupled plasma mass spectrometry. The mass of lead measured was then used to calculate the lead loading per area sampled in µg/ft2. We compared our dust wipe results with the dust-lead hazard standard for house floors established by the US Environmental Protection Agency (EPA) (10 µg/ft2). 28
Statistical Analysis
We analyzed questionnaire responses and lead dust levels for significant differences across industries with sufficiently large sample sizes. We compared the frequencies of questionnaire responses for the current use of best practices for reducing take-home lead exposures among the automobile repair, lead-based paint remediation, and scrap metal recycling industries using Fisher exact tests.
Because the distribution of the original lead dust levels was right skewed, we performed all statistical analyses on log-transformed lead dust levels, which had an approximately normal distribution. We used univariate linear regression to generate point estimates and 95% CIs of log-transformed lead dust level (µg/ft2) for the automobile repair, firing range, lead acid battery recycling, and scrap metal recycling industries. We used linear mixed-effect models to generate point estimates and 95% CIs of log-transformed lead dust levels for each questionnaire response for all industries combined as well as separately for the 2 industries with sufficient sample size—automobile repair and recycling (scrap metal and lead battery combined)—while controlling for correlations among samples taken from multiple vehicles at the same establishment. We considered nonoverlapping 95% CIs of predicted log-transformed lead dust levels across each industry or between questionnaire responses significant. Using nonoverlapping 95% CIs is approximately equivalent to setting the type I error rate at .05. We completed analyses using SAS version 9.4 (SAS Institute, Inc).
Results
Establishment Identification
We identified a total of 320 establishments with potential lead exposure: 200 in Genesee County, 94 in Ingham County, and 26 demolition contractors from around the state who had performed work in Genesee County (Table 1). Overall, questionnaires were completed at 37.2% (n = 119) of establishments, and at least 1 lead sample was gathered from 12.2% (n = 39) of establishments. Of establishments that were identified but did not participate, 60.2% (n = 121) did not participate because we lacked a successful contact or response, and 39.8% (n = 80) refused to participate when contacted.
Identification and participation of 320 establishments in industries with the potential use of, and worker exposure to, lead, Genesee and Ingham counties, Michigan, 2018-2020 a
One employee at each establishment was asked to complete a questionnaire reflecting the establishment-wide use of work practices and policies that would mitigate the amount of lead dust leaving the workplace. All values are numbers.
Questionnaires
Of the 119 establishment-level questionnaires completed, a large proportion (43.8%) of establishment representatives said they did not know how often employees worked with lead, if at all, and 18.1% said employees worked with lead daily (Table 2). Only 39.8% of establishments said that workers were trained on the hazards of working with lead. Many workplaces reported their workers always (53.0%) or sometimes (24.8%) wore gloves, wore clothing entirely (45.7%) or partially (21.6%) provided by their employers, and laundered their work clothing through a professional service (55.7%). Most establishments did not (76.1%) provide a shower for their employees to use at work and reported their workers often did not change clothes (49.2%) or shoes (50.4%) before leaving the workplace and drove their personal vehicle (92.2%) to and from work. Forty-one percent of workplaces were aware of at least 1 employee who lived at home with a child aged <6 years.
Results of a questionnaire administered to establishments in industries with the potential use of, and worker exposure to, lead, Genesee and Ingham counties, Michigan, 2018-2020 a
One employee at each establishment was asked to complete a questionnaire reflecting the establishment-wide use of work practices and policies that would mitigate the amount of lead dust leaving the workplace; 119 of 320 establishments identified participated in the study.
Percentages calculated as the number of responses with a given answer divided by the total number of nonmissing responses.
Analysis of questionnaire data for the industries with a sufficient number of responses for analysis (automobile repair, lead-based paint remediation and inspection, and scrap metal recycling) showed a significant relationship between the distribution of responses and industry for several practices. A higher percentage of responses from the automobile repair and scrap metal industries (52.8% and 46.2%, respectively) indicated that respondents did not know how often employees worked with lead compared with responses from the lead-based paint industry (6.7%); training on lead hazards was more common in the lead paint remediation (80.0%) and scrap metal (53.3%) industries compared with auto repair (26.9%); the use of clothing at least partially provided by employers was more frequent in the auto repair (76.3%) and scrap metal (66.7%) industries than in lead paint remediation (25.0%); employees in the lead paint remediation industry were more likely to launder their clothes at home (80.0%) than employees in the auto repair (31.3%) and scrap metal (46.7%) industries; the availability of a shower was more prevalent in the lead paint remediation industry (50.0%) than in the auto repair (10.1%) and scrap metal (20.0%) industries; and, finally, although most responses from all 3 industries indicated employees used personal vehicles to travel to work, 16.7% of responses from the lead paint remediation industry indicated employees used employer vehicles, compared with 3.9% in auto repair and none in scrap metal recycling.
Dust Sampling
We collected 60 dust wipe samples from the floor mats in employee vehicles at 39 establishments (Table 3). We took multiple samples from 13 establishments, including samples taken from 6 employee vehicles at the lead acid battery recycling establishment. The results of all wipes ranged from 5.7 to 84 000 µg/ft2 and were heavily right skewed with a geometric mean of 234 µg/ft2 and a geometric SD of 6.73. Fifty-seven (95.0%) samples were above the EPA’s dust-lead hazard standard for house floors of 10 µg/ft2, with 68.3% of samples >100 µg/ft2 and 23.3% of samples >1000 µg/ft2, 10 and 100 times the dust-lead hazard standard, respectively. Univariate regression of the log-transformed sample results by industry revealed that the log-transformed values collected from the lead acid battery recycling industry were significantly higher than the overall mean of the log-transformed values.
Results of lead dust sampling in employees’ personal vehicles at 39 establishments in industries with the potential use of, and worker exposure to, lead, Genesee and Ingham counties, Michigan, 2018-2020 a
Abbreviation: EPA DLHS, Environmental Protection Agency dust-lead hazard standard.
Dust samples (n = 60) were taken from the personal vehicles of all employees who were at the workplace during the visit and were willing to participate.
US EPA DLHS is 10 µg/ft2. 26
Significantly different from overall mean of log-transformed values; P = .002.
When we examined the relationship between dust wipe samples and the corresponding questionnaires from the same establishment for all industries, automobile repair establishments, and recycling (scrap metal and lead battery combined), we found that the use of protective practices was associated with higher sample geometric means when all samples were combined (Table 4). Conversely, among auto repair establishments, we found that the use of best practices was generally associated with lower sample geometric means. The identification of any such trends in recycling industries was precluded by the large number of possible answers for which there were no responses. Linear mixed-effect regression found that none of the questionnaire results were associated with significant differences in lead dust samples except for the question on how often employees work with lead in the overall pooled results, with those reporting daily use of lead having significantly higher log-transformed lead dust samples than those reporting using lead “a couple of times per week.”
Relationship between dust wipe samples and the corresponding questionnaires from the same establishment for all industries, automobile repair establishments, and recycling (scrap metal and lead battery combined), Genesee and Ingham counties, Michigan, 2018-2020 a
Abbreviation: —, does not apply.
One employee at each establishment was asked to complete a questionnaire reflecting the establishment-wide use of work practices and policies that would mitigate the amount of lead dust leaving the workplace; 119 of 320 establishments identified participated in the study. Dust samples (n = 60) were taken from the personal vehicles of all employees who were at the workplace during the visit and were willing to participate.
Response percentages calculated as the number of responses with a given answer divided by the total number of responses in that industry group.
The predicted means of the log-transformed lead sample values for these responses differed significantly; P < .001.
Discussion
In this project, we designed and piloted a program for assessing the potential for take-home lead exposures from work in 2 Michigan counties. This initiative identified 320 establishments in these 2 counties in industries with potential workplace lead exposure. Although 56% of the surveyed establishments did have employees working with, or exposed to, lead at least occasionally, only 40% of establishments trained workers on lead hazards, and many did not implement practices for reducing the potential for take-home lead exposures. Dust sampling on the floors of employee vehicles across all industry types suggested the potential for take-home lead exposures in the home: all vehicles sampled had measurable lead, and nearly all samples were higher than the EPA dust-lead standard for house floors, with many samples containing lead levels much higher than the standard. These findings, coupled with 41% of respondents knowing that employees lived with young children, suggest that take-home lead exposures are likely occurring in these counties. The high percentage of workplaces (44%) that did not know if employees worked with lead indicates a need to educate the owners and workers in these industries where there is known potential for lead exposure. Finally, comparing sampling results with questionnaire responses in the auto repair industry suggests that the implementation of recommended practices holds promise for reducing the amount of lead dust leaving the workplace.
These findings build upon previous research into the potential for lead originating in occupational settings to produce contamination of personal vehicles and homes. The high proportion of respondents who did not have measures to prevent lead dust from leaving the workplace is consistent with previous reports of workers wearing personal clothing into and out of workplaces; employers not providing or enforcing the use of personal protective equipment, uniforms, and showers; and even a complete lack of training on lead hazards in the workplace.1,9,11,29,30 Previous studies that sampled lead dust on the floors of employee vehicles found a median of 1570 µg/ft2 for workers in lead paint remediation and metal recycling industries, 9 a mean of 40.3 µg/ft2 for workers in the lead paint remediation industry, 2 and geometric means of 818 µg/ft2 and 177 µg/ft2 for bridgeworkers.29,31 The overall geometric mean of 234 µg/ft2 we observed is in the middle of these previous measurements, although we found that the industry with the highest levels, lead acid battery recycling (geometric mean = 3227 µg/ft2), was notably higher. Significant decreases in steering wheel wipe samples have been associated with increasing use of preventive practices, reflecting the trend seen here in auto repair establishments. 29 Additional approaches to controlling lead dust, including engineering controls such as ventilation, may be necessary to reduce take-home lead levels in industries with particularly high lead exposures, such as lead battery and scrap metal recycling.
Although this study was not able to directly compare lead dust levels in employee vehicles and homes, a previous study that measured lead dust levels in the vehicles and homes of construction workers found that the levels in homes were approximately 1 to 2 orders of magnitude lower than lead dust levels in vehicles. 1 If such a dilution were applicable to the results here, an estimated 23% to 68% of workers would still have lead dust levels in their home above the EPA standard. Furthermore, it is possible that children are exposed to lead dust in the vehicle itself, an environment that has been previously linked to instances of child lead poisoning. 9 No EPA standard exists for lead dust in vehicles, and the standard for lead dust in homes is likely not a fully accurate comparison of risk in the absence of accompanying measurements of home dust and given that children are likely to spend much more time in contact with the floor of a home than with the floor of a vehicle. In the workplace, Michigan OSHA has recommended a less stringent 200 µg/ft2 as a guideline for determining whether an employer has maintained surfaces free from lead contamination. 32 Notably, the overall and industry-specific geometric means that we measured, except for that of auto repair, were above the Michigan OSHA-recommended level.
Limitations
This study had several limitations. First, it was limited by the voluntary nature of participation. Although establishments across industries were identified, participation was much higher among automotive repair and scrap metal recycling establishments than among lead paint remediation establishments and contractors, likely because the former were physical establishments that could be visited and recruited in person, whereas the latter involved contact and recruitment by telephone because of the lack of a physical storefront. Because most nonparticipating establishments were not successfully contacted, no information was available to explain participation patterns. Because of the low participation rates by certain types of employers, our study may have underreported the potential for take-home lead exposure in industries such as lead paint abatement, industrial paints and coatings, firing ranges, and other difficult-to-recruit establishments. This hurdle is important to overcome because of reports of lead poisoning among children of workers in some of these industries. Second, we relied on a single employee’s responses to the questionnaire as representative for the establishment. This limitation likely led to some misclassification because the employee may not have had full knowledge of the establishment’s lead safety plan and/or employee adherence, especially if the employee did not perform lead-related tasks. Third, we visited an establishment only once. Continued monitoring of establishments would allow further characterization of the temporal variation in the amount of lead leaving workplaces and the uptake of protective practices after initial visits; however, follow-up visits were not able to be completed during this pilot project.
Conclusions
The approach used here offers a model for local health departments to investigate possible take-home lead exposures in their geographic jurisdiction across multiple industries. Such an approach is needed because data collected by ABLES suggest take-home exposures are likely occurring. 16 Once establishments are identified and an initial survey of work practices and lead dust leaving the workplace is completed, as done here, industries, specific establishments, or even individual workers can be identified for monitoring and intervention and for blood lead testing for workers and their families. This type of initiative would align with recent calls to coordinate child and adult blood lead surveillance 33 (a suggestion made in part to help identify children whose parent’s work is an important contributor to their lead exposure) and would integrate multiple approaches for reducing take-home lead exposures, including the control of lead dust in the workplace, the adoption of work practices for reducing the amount of lead dust leaving the workplace, 34 and methods for removing lead dust from the home 35 (and vehicles). Establishments with a small number of employees who were identified in our project are unlikely to be inspected by OSHA; if inspected, the establishment may not use lead at a high enough exposure level (ie, an airborne concentration of lead of ≥30 µg/m3 averaged during an 8-hour period) to require compliance with the OSHA lead standard. In addition, some establishments were not under OSHA’s jurisdiction, such as private gun clubs, whose members volunteer to do tasks and have no paid employees, further supporting the need for outreach to these establishments.
Despite evidence linking parents’ occupations to child lead poisoning, initiatives to address take-home lead are not routine components of childhood lead programs. The program described here successfully identified establishments as potential sources of take-home lead exposure and characterized both the extent of lead dust leaving the workplace and the current use of practices meant to mitigate it. We have developed a guide for health departments to conduct evaluations of take-home lead in their jurisdictions based on this pilot. 18 Our program was carried out by an environmental sanitarian, a common job in health departments. The primary hurdles in implementing this program—our reliance as an academic institution on the voluntary participation by employers and our inability to tie assessed outcomes to lead levels in household dust or to child blood lead levels—could be overcome by health departments with regulatory authority and by incorporating our approach into existing programs that include ongoing child blood lead surveillance and home inspections.
Footnotes
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Michigan State University conducted this project with funding obtained from the Michigan Child Lead Exposure Elimination Commission Innovation Grant program.
