This chapter describes occupational exposure guidelines for lead. The US standards and guidelines of the Occupational Safety and Health Administration (OSHA), the National Institute for Occupational Safety and Health (NIOSH), and the American Conference of Governmental Industrial Hygienists (ACGIH®) are presented first and then guidelines of other countries, including those of the European Union, Germany, and the United Kingdom. Features common to the guidelines include an airborne exposure limit as an 8-hour time-weighted average (TWA) and a recommended blood lead level (BLL) to prevent adverse health effects. Table 2-1 presents a comparison of the various occupational-exposure guidelines.
Occupational Safety and Health Administration Lead Standard
OSHA was created in 1970 on passage of the Occupational Safety and Health Act (OSHAct), Public Law 91-596. The OSHAct became effective on April 28, 1971, and authorized the federal government to establish and enforce standards for occupational safety and health. The intention of the OSHAct was to ensure that all employees in the United States had safe working conditions. The OSHAct also required the head of each federal agency (except the US Post Office) to establish an occupational safety and health program that is consistent with the standards promulgated under the act.
The OSHA lead standard for general industry (29 CFR 1910.1025) was promulgated on November 14, 1978. It applied to all occupational exposures to lead except those associated with construction or agricultural work. The key components of the lead standard were the setting of a permissible exposure limit (PEL) of 50 μg/m3 as an 8-hour TWA and the institution of a medical surveillance program for all employees who are or may be exposed above the 8-hour TWA action level (30 μg/m3) for more than 30 days per year.
TABLE 2-1 Occupational-Exposure Guidelines for Lead
|Agency||Air-Exposure Guideline (8-h time-weighted average)||Recommended Limit for Blood Lead Level||Year Approved|
|Occupational Safety and Health Administration||50 μg/m3||40 μg/dL||1978|
|National Institute for Occupational Safety and Health||50 μg/m3||60 μg/dL||1978|
|American Conference of Governmental Industrial Hygienists||50 μg/m3||30 μg/dL||1987 (air) 1995 (blood)|
|European Council Directive 98/24||150 μg/m3||70 μg/dL||1998|
|European Union Scientific Committee on Occupational Exposure Limits||100 μg/m3||30 μg/dL||2002|
|German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area||None, because probably carcinogenic in humans||40 μg/dL for men and women over 45 years old 10 μg/dL for women under 45 years old||2006|
|United Kingdom Health and Safety Executive||150 μg/m3||25 μg/dL for women of reproductive age 40 μg/dL for people 16-17 years old 50 μg/dL for all other employees||2002|
In the years preceding the promulgation of the OSHA lead standard, airborne lead exposure limits of 150-200 μg/m3 and BLLs of 80 μg/dL were followed (43 Fed. Reg. 52952 ). Data that emerged in the middle 1970s suggested that those levels were too high and should be reduced.
OSHA provided the following rationale for the final standard (40 Fed. Reg. 52952 ):
Health Effects: OSHA relied on studies that reported adverse health effects in conjunction with BLLs and considered both effects from acute exposure and, to the extent that they were known, effects of long-term lead exposure. In
addressing the array of adverse health effects, OSHA cited five stages of a disease process—“normal, physiological change of uncertain significance, pathophysiological change, overt symptoms (morbidity), and mortality” (p. 52594) and recognized that there was not a sharp distinction between stages but rather that they are on a continuum. OSHA went on to state that an adopted standard “must prevent pathophysiological changes from exposure to lead”. In questioning whether both “clinical and subclinical effects” of exposure should be considered, OSHA judged that those terms represented “vast over-simplifications of a disease process and, therefore … avoided their use in the final standard” (p. 52963). OSHA regarded subclinical effects to be the “early to middle stages in a continuum of disease development process” (p. 52963).
OSHA summarized key studies on heme-synthesis inhibition (inhibition of the enzymes delta-aminolevulinic acid dehydrogenase [ALAD] and ferrochelatase) and anemia; on neurologic effects (central nervous system symptoms, behavioral symptoms, peripheral nerve effects, and results of nerve-conduction testing); on renal effects; and on reproductive effects. Except for reproductive effects, the evidence demonstrated adverse pathophysiologic effects at BLLs over 40 μg/dL; thus, 40 μg/dL was considered the upper acceptable limit. Concerning reproductive effects and effects on children (hyperactivity at BLLs as low as 25 μg/dL), “OSHA concludes that in order to protect the fetus and newborn from the effects of lead on the nervous system, blood lead levels must be kept below 30 μg/100 g [30 μg/dL]” for workers who wish to plan pregnancies (40 Fed. Reg. 52960 ). OSHA also acknowledged at the time that for many of the adverse health effects there was evidence of a dose-response relationship but that the “no-effect level” remained to be determined.
Air-Blood Relationships: Although industry representatives maintained that BLLs could not be correlated with or predicted from air lead concentration, OSHA judged that despite some data limitations the collective data could be used to make estimates. OSHA described some studies that provided linear models and regression analyses. It relied predominantly on a physiologic model originally developed by S. R. Bernard and adapted by the Center for Policy Alternatives (CPA) that “combines experimentally observed properties of mammalian lead transport and metabolism, including consideration of the dynamics of blood lead response to long term exposure” (40 Fed. Reg. 52961 ). The model also accounted for “the observed physical properties of airborne particulates encountered in the workplace, in order to produce a complete and accurate picture of the response of blood lead levels to particulates” (40 Fed. Reg. 52967 ), and CPA included specific consideration of individual variability in response to air lead. The model was applied to exposures at air concentrations of 50, 100, and 200 μg/m3, and the results were used to predict the percentage of workers that would fall within different BLLs. The results demonstrated the benefit of setting an air concentration of 50 μg/m3 to reduce the number of workers who had predicted BLLs over 40 μg/dL. (See Chapter 3 for the committee’s evaluation of the model and its assumptions.)
Approach to the Rule: OSHA’s reasons for placing primary reliance on an air PEL for compliance and citations rather than on biologic monitoring included these: evaluation of the industrial environment focused on the direct measurement and control of sources of lead exposure whereas biologic monitoring was designed to ascertain problems of individual workers and was an indirect measure, or check, of the control of lead; biologic monitoring was not feasible for compliance and citation purposes; and biologic monitoring alone might not provide adequate protection for workers, because excessive exposure to lead would not result immediately in excessive BLLs.
Permissible Exposure Limit
The lead standard requires employers to ensure that no employee is exposed above the PEL. In 1971, OSHA set the initial PEL for lead at 200 μg/m3 as an 8-hour TWA. The PEL was based on American National Standards Institute consensus standard z37.11-1969. The consensus standard did not provide any justification for its level of 200 μg/m3 (43 Fed. Reg. 52952 ). OSHA also used the ACGIH threshold limit value (TLV®) as a national consensus standard to establish the initial PEL (Public Law 91-596). The 1968 TLV for lead was also 200 μg/m3 (43 Fed. Reg. 52952 ). OSHA was required in the OSHAct to set standards by using national consensus standards within 2 years of the OSHAct’s becoming effective (Public Law 91-596).
In 1973, NIOSH recommended that the PEL be lowered to 150 μg/m3. On October 3, 1975, OSHA proposed a new PEL of 100 μg/m3. After the proposal was made, OSHA requested comments, data, and opinions on the lower PEL. Hearings were held in multiple locations in 1977. In light of the information received during the comment period and the hearings, a new lead standard received final certification on August 8, 1978 (43 Fed. Reg. 52952 ).
The OSHA lead standard set the PEL at 50 μg/m3 as an 8-hour TWA, which was technically feasible for industry. In OSHA’s opinion, a lower air lead concentration of 40 μg/m3 would not offer a substantial benefit compared with 50 μg/m3.
An action level is an air concentration that triggers the initiation of required activities, such as exposure monitoring and medical surveillance. OSHA defined the action level for lead as “employee exposure, without regard to the use of respirators, to an airborne concentration of lead of 30 μg/m3 averaged over an 8-hour period” (29 CFR 1910.1025(b)). Exposure monitoring is performed to determine whether employees are exposed to lead above the action level. Some requirements are instituted when the action level is exceeded (see the section “Medical Monitoring” below).
The lead standard requires that employers monitor their employees to determine their personal exposure to airborne lead. The monitoring must be done for the full work shift of at least 7 continuous hours. It must be done for every shift in which employees were exposed to lead and an evaluation of the data must assume that employees were not wearing respirators. When personal exposures are below the action level (30 μg/m3), the result must be documented in writing, and no additional monitoring is required. When personal exposures exceed the action level but are below the PEL, additional personal monitoring is required every 6 months until two consecutive measurements, collected at least 7 days apart, are below the action level. For personal monitoring results above the PEL, additional monitoring must be done quarterly. The sampling frequency can be reduced to every 6 months only when two consecutive measurements, collected at least 7 days apart, are below the PEL (29 CFR 1910.1025(d)).
Engineering and Work-Practice Controls
Engineering and work-practice controls must be implemented whenever employees are exposed above the PEL for more than 30 days per year. The controls include the requirement for a written compliance program to reduce personal exposures to below the PEL. If engineering and work-practice controls do not reduce exposures to below the PEL, respirators must be worn. If mechanical ventilation is used to control exposures, the ventilation system must be evaluated quarterly for its effectiveness in controlling exposures (29 CFR 1910.1025(e)).
Respirator Protection and Personal Protective Equipment
When respirators are required, a respiratory-protection program must be implemented in accordance with 29 CFR 1910.134. The respirators can be half-mask, full-facepiece, or powered air-purifying respirators. High-efficiency particulate air-equivalent (HEPA-equivalent) filters are required (29 CFR 1910.1025(f)).
Personal protective equipment must be provided at no cost to employees when exposures exceed the PEL. The equipment may include face shields, vented goggles, and disposable shoe coverlets. The employer is responsible for cleaning or disposing of the equipment (29 CFR 1910.1025(g)).
Housekeeping and Hygiene Facilities and Practices
All surfaces must be kept as free as practicable of any accumulations of lead. Surfaces cannot be cleaned by using compressed air; vacuuming is the preferred method of cleaning. When vacuuming is shown not to be effective, shoveling or dry or wet sweeping may be used (29 CFR 1910.1025(h)).
When exposures exceed the PEL, an employer must provide dedicated changing rooms, a lunchroom under positive pressure, and shower facilities. Food, beverages, and tobacco products cannot be present, consumed, or used, and cosmetics cannot be applied anywhere in the facility, except in the changing room, lunchroom, or shower areas. Changing rooms must separate street clothes from contaminated work clothing in a way that prevents cross-contamination. Employees are not permitted to enter the lunchroom without removing lead from their protective work clothing. Employees must wash their hands and face before eating, drinking, smoking, or applying cosmetics, and they must shower at the end of each work shift (29 CFR 1910.1025(i)).
The following are the key points of the OSHA lead standard for general industry regarding medical surveillance (29 CFR 1910.1025(j)):
• The employer institutes a medical surveillance program for all employees who are or may be exposed at or above the air action level of 30 μg/m3.
• Monitoring is performed by or under the supervision of a licensed physician.
• A full medical examination and consultation shall be made available to an employee
Before the first assignment to an area that has lead at or above the action level.
At least once a year for an employee who had a BLL of 40 μg/dL or over at any time during the preceding 12 months.
As soon as possible on notification by an employee that he or she has developed signs or symptoms of lead intoxication, desires medical advice concerning the effects of lead (past or current) and the ability to procreate a healthy child, or who has difficulty in breathing during respirator fit test or use.
• A full medical examination will include
A detailed work and medical history.
A thorough physical examination.
Measurement of blood pressure.
Analysis of BLL, hemoglobin and hematocrit, erythrocyte indexes, peripheral smear morphology, zinc protophorphyrin (ZPP), blood urea nitrogen and creatinine, urinalysis with microscopic examination, and any other tests that a physician thinks are appropriate, including a pregnancy test or laboratory evaluation of male fertility if requested by the employee.
• Biologic monitoring (for all employees who are working at or above the action level) and medical removal protection:
BLL and ZPP levels evaluated every 6 months.
Removal from work of an employee who has a BLL of 60 μg/dL or higher or who has an average BLL of the last three tests (or the average of all BLLs over the preceding 6 months) of 50 μg/dL or higher.
Evaluation of BLL and ZPP levels monthly during medical-removal period.
Removal not needed when the last BLL was under 40 μg/dL.
Temporary removal of an employee who is working at or above the action level and has a medical condition that makes the employee more susceptible to the risk posed by lead.
• Medical-removal protection benefits include o Up to 18 months of medical-removal-protection benefits on each occasion when an employee is removed.
Employer’s maintenance of earnings, seniority, and other employment rights as though the employee has not been removed.
Employee Information and Training
Employee training is required whenever there is a potential for exposure to airborne lead. Training must include the information provided in Appendixes A and B of 29 CFR 1910.1025. When employees are exposed above the action level, they must be informed of the content of the lead standard, and a training program must be initiated. Training is required each year, and the employer must make available to all employees a copy of the OSHA lead standard and its appendixes (29 CFR 1910.1025(l)).
National Institute for Occupational Safety and Health Criteria
NIOSH was created in 1970 by the OSHAct and established in the Department of Health Education and Welfare, which became the Department of Health and Human Services, to carry out the duties of the OSHAct assigned to the secretary of health and human services. Those duties include research, experiments, and demonstrations related to occupational safety and health (Public Law 91-596). NIOSH first published its Criteria for a Recommended Standard: Occupational Exposure to Inorganic Lead in 1973. After an OSHA proposal to revise the occupational health standard for inorganic lead in 1976, NIOSH revised its criteria document in 1978 and lowered its recommended 10-hour TWA for airborne lead from 150 to 100 μg/m3 and its recommended maximum BLL from 80 to 60 μg/dL (NIOSH 1978).
NIOSH noted that testimony at OSHA hearings indicated that “based on about 10 studies … to keep blood lead levels in male workers below 40
[μg/dL], air lead exposures have to be kept under 50 μg/m3” (NIOSH 1978, p. XII-14). In addition, data from the General Motors plant in Muncie, Indiana, indicate that “if yearly average personal sampler air lead exposure … is kept below 100 μg/m3, yearly average blood leads in over 90% of workers will be under [60 μg/dL]. Similarly, if yearly average personal sampler air leads … are kept under 50 μg/m3, yearly average blood leads will be 40 [μg/dL] or lower for over half of the workers. One of the greatest impacts of reducing lead exposure in air from 200 to 100 μg/m3 is a great increase in the number of workers with blood lead levels 40 [μg/dL] or lower” (NIOSH 1978, p. XII-15).
NIOSH also notes that the relationship between air lead and BLL may not be linear over the whole range of exposures: “Incremental changes in air lead exposure in the range up to 100 μg/m3 produce greater increases in blood lead than do similar increases in the range from 100-200 μg/m3” (NIOSH 1978, p. XII-115).
At the time, the OSHA proposal was for an action level of 50 μg/m3, which NIOSH endorsed in its criteria document “as a future goal to provide greater assurances of safety” (NIOSH 1978, p. XII-19). That air level would keep BLLs at about 40 μg/dL or lower in virtually all workers, protecting against “subclinical” effects of lead. NIOSH also endorsed a “vigorous medical surveillance program” for workers exposed above the action level but below the proposed maximum air lead concentration of 100 μg/m3. NIOSH estimated that “even at the proposed air standard of 100 μg/m3, less than half of the workers will have blood lead levels above 40 [μg/dL]” (NIOSH 1978, p. XII-19).
In 1997, NIOSH published a Federal Register notice (62 Fed. Reg. 55407 ) requesting comments and information relevant to the potential health risks associated with occupational exposure to inorganic lead at or below the OSHA PEL of 50 μg/m3. To date, however, no additional recommendations have been proposed by NIOSH.
American Conference of Governmental Industrial Hygienists Guidelines
ACGIH is a not-for-profit organization with a mission for advancing occupational and environmental health and safety through the development and publication of scientific guidelines and research. The organization manages several scientific committees that consist of volunteers in government agencies, academic institutions, labor unions, and industrial companies. The committees are the Threshold Limit Values for Chemical Substances Committee, which develops TLVs for airborne chemical substances and materials; the Biological Exposure Indices (BEIs®) Committee for biologic indicators of exposure to chemical substances and materials; and the Threshold Limit Values for Physical Agents Committee, which recommends guidelines for physical hazards, such as noise, temperature, and pressure. Each committee recommends exposure guidelines to the ACGIH Board of Directors, which ensures that all organizational procedures and policies have been followed before ratification. The recommendations
The lead BEI was first proposed by ACGIH in 1985 and adopted in 1987. Levels were set for lead concentrations in blood (50 μg/dL), urinary creatinine (150 μg/g), and ZPP in blood (250 μg/dL for erythrocytes or 100 μg/dL for blood after 1 month of exposure). In 1995, a new BEI BLL was adopted for lead (30 μg/dL); other indicators in urine and blood were dropped. A notation B (background) was included, indicating that “the determinant may be present in biological specimens collected from subjects who have not been occupationally exposed, at a concentration which could affect interpretation of the result. Such background concentrations are incorporated into the BEI value” (ACGIH 2012). In 1998, the B notation was removed “because the U.S. population average blood lead concentration … is now less than 3 [μg/dL]” (ACGIH 2001a, p. 8).
The goal of the current BEI for lead in blood is to lower the likelihood of several adverse health outcomes, including
• Psychologic and psychomotor effects that appear to occur at BLLs over 30 μg/dL.
• Changes in nerve conduction and latency intervals that appear to occur at BLLs over 30 μg/dL.
• Decrements in hematologic reserve capacity (one study) at BLLs over 40 μg/dL.
• Increased blood pressure and incidence of hypertension; effects at BLLs under 30 μg/dL expected to be very small.
• Renal impairment with minor effects reported at BLLs under 30 μg/dL and increased proteinuria at BLLs of 40 μg/dL.
• Spontaneous abortions and effects on male fertility that appear to occur at BLLs over 30 μg/dL.
• Decreased length of gestation and decreased birth weight; expert reviews indicate that effects appear to be associated with BLLs over 30 μg/dL.
ACGIH (2001a) notes that some studies have found effects at levels below the BEI, but these were short-lived, did not affect functional capacity, or were contradicted by other studies. The documentation also notes that women and men of childbearing potential who have BLLs over 10 μg/dL may be at risk for having a child who has levels greater than the current guideline from the Centers for Disease Control and Prevention, 10 μg/dL.
A TLV 8-hour TWA of 150 μg/m3 for lead and inorganic compounds in air was first adopted in 1946 and has undergone several revisions. The most recent revision in 1995 recommended a TLV-TWA of 50 μg/m3. ACGIH classifies lead as a confirmed animal carcinogen with unknown relevance to humans. The TLV-TWA was based on the ACGIH BEI for lead and “intended to minimize the potential for adverse health effects that may include blood dyscrasias, reduced nerve conduction velocities, peripheral neuropathies, a possible kidney
dysfunction, spermatogenesis, impaired intellectual development in children exposed to lead during gestation, and carcinogenicity” (ACGIH 2001b, p. 1). ACGIH notes that “blood values, rather than work environment air lead concentrations, are most strongly related to health effects…. The TLV-TWA is intended to maintain worker blood lead levels below the BEI of 30 μg/dL. Maintaining blood levels at or below this level must also focus on control of exposure to non-airborne sources of lead, such as by meticulous plant environment housekeeping, strict personal cleanliness, and prohibition of eating, drinking, and smoking in lead-contaminated areas” (ACGIH 2001b, p. 1).
Derivation of the appropriate air lead concentration used the steepest slope (0.19 μg/dL of blood per μg/m3 of air) found in the literature (slopes ranged from 0.03 to 0.19 μg/dL of blood per μg/m3 of air). A TLV-TWA of 50 μg/m3 would be expected to result in a BLL of about 9.5 μg/dL. ACGIH proposes that this air concentration will be sufficient to prevent a BLL of 30 μg/dL (the BEI) if other sources (community or noninhalation workplace exposures) are adequately controlled.
European Council Directive 98/24
The European Council Directive 98/24/EC of 1998 on the protection of the health and safety of workers from risks related to chemicals has “binding occupational exposure limit values” (a maximum allowable TWA of lead in air) and “binding biological limit values and health surveillance measures” (BLLs that should not be exceeded) for lead (Council 1998). The binding occupational exposure limit is 150 μg/m3 (8-hour TWA), and the biologic limit is 70 μg/dL. Medical surveillance is indicated if a worker is exposed to lead at 75 μg/m3 (TWA over a 40-hour week) or if a worker’s BLL is over 40 μg/dL. Taylor et al. (2007) conducted a survey of how the directive has been implemented in 14 EU countries and found disparities in its implementation. Most of the countries have implemented the binding occupational exposure limit for lead, but five countries (Denmark, Finland, France, Germany, and Poland) have set lower limits. Most countries have established binding biologic limits lower than the one specified in the directive, with a range of 20-60 μg/dL. Two countries (Belgium and the Netherlands) allow BLLs as high as 80 μg/dL provided that other measures of biologic effects are below certain limits. Most of the 14 EU countries have adopted the directive’s biologic triggers for medical surveillance.
European Union Scientific Committee on Occupational Exposure Limits
The European Union Scientific Committee on Occupational Exposure Limits (SCOEL) recommends a lower biologic limit for lead than European
Council Directive 98/24/EC of 1998. The SCOEL recommends a BLL of 30 μg/dL to prevent adverse neurobehavioral effects and signs of male reproductive toxicity that occur at BLLs of 40 μg/dL and higher. The SCOEL could not identify a threshold for impairment of cognitive development in newborns and infants and indicated that “exposure of fertile women to lead should … be minimised” (SCOEL 2002, p. 13).
The European Union also has an 8-hour TWA of 100 μg/m3 for inorganic lead, including lead fumes and dusts with particle sizes below 10 μm. The SCOEL documentation conclusion that the carcinogenicity of lead most likely depends on “indirect, rather than on direct genotoxic mechanisms” implies a “practical threshold for the carcinogenic effects, and would argue in favour of the possibility of setting a health-based OEL [occupational exposure limit] for lead” (SCOEL 2002, pp. 8-9). The air lead concentration is considered consistent with the biologic limit and was derived from field studies of lead-battery workers by Lai et al. (1997) and others (e.g., Kentner and Fischer 1994).
German Commission for the Investigation of Heath Hazards of Chemical Compounds in the Work Area
The Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area (MAK Commission) is in the Deutsche Forschungsgemeinschaft (German Research Foundation), a private organization for science and research. The commission is responsible for determining the current state of research regarding workplace hazardous-chemical health risks and for advising public authorities about these risks. The MAK Commission proposes MAK values (maximum concentrations at the workplace) and BAT values (biologic tolerance values) for volatile chemicals and dusts and proposes procedures for analyzing these substances. Each year, the MAK and BAT proposals are presented to the German federal minister of labor and social affairs; these are reviewed by the ministry’s Committee on Hazardous Substances, which determines whether they should be included in the Hazardous Substances Ordinance. The MAK Commission also develops and publishes detailed scientific documentation for each of its MAK and BAT values.
From 1977 to 2006, the German MAK for lead and inorganic compounds was 100 μg/m3 (inhalable). The cancer classification was 3B (evidence of carcinogenicity in animal or in vitro studies without sufficient evidence for classification in other categories). The BAT, adopted in 2000, was 40 μg/dL in blood, with a pregnancy-risk group B notation (probable risk of damage to embryo or fetus even when the BAT or biologic guideline value [BLW] is observed). Those levels were expected to protect men and women from central nervous system effects, which are first seen at average BLLs of 40 μg/dL, and to prevent cognitive deficits in offspring of exposed women. There was no clear threshold for the latter; effects were expected to be minimal if maternal BLLs were under 30 μg/dL (DFG 2009).
After a 2006 reclassification of inorganic lead compounds as category 2A carcinogens (probably carcinogenic in humans) by the International Agency for Research on Cancer, a German category 2 cancer notation was assigned to these compounds, and the MAK and BAT were withdrawn. German policy states that “substances carcinogenic in man or experimental animals are classified in categories 1 or 2 and are not assigned MAK or BAT values.” Thus, there is no longer a German MAK for lead, because “it is not possible to derive a no observed adverse effect level for the clastogenic effect of lead and its inorganic compounds…. Therefore, no threshold value can be established” (DFG 2009, p. 188).
A BLW is used when a BAT value cannot be established, as for carcinogenic or suspected carcinogenic substances. The BLW for lead is 40 μg/dL for all men and women older than 45 years old and 10 μg/dL for women younger than 45 years old. The bases for those values are the prevention of neurotoxic effects and minimization of reproductive toxic effects (DFG 2005). Lead and its inorganic compounds are considered to be in pregnancy-risk group B, which indicates probable risk of damage to an embryo or fetus even when the BLW is observed.
United Kingdom Health and Safety Executive
The Health and Safety Executive (HSE) enforces the Health and Safety at Work Act of 1974, the primary legislation governing occupational health and safety in the UK. The HSE is a nondepartmental public body with Crown status and is accountable to the ministers of the Department for Work and Pensions. The HSE regulates work-related health and safety in the UK in partnership with local authorities; its mission is the prevention of workplace death, injury, and ill health. Within the HSE, the Health and Safety Laboratory is responsible for research, scientific, and forensic services, including technical support of investigations.
In 2002, the UK HSE issued updated guidance regarding the Control of Lead at Work Regulations (HSE 2002). Workplace exposure to lead is considered significant if levels exceed half the occupational exposure limit of 150 μg/m3 for lead other than lead alkyls, there is substantial risk of ingestion of lead, or there is risk of skin exposure to forms of lead that are readily absorbed through the skin. Significant exposures require protective clothing for employees, air monitoring, and employee medical surveillance. Where engineering controls are not feasible or effective, respiratory protection is required. High standards of personal hygiene—including washing facilities and policies that forbid eating, drinking, or smoking in lead-contaminated areas—are required for all employees.
The HSE guidance notes that “there is not necessarily a strong relationship between the amount of lead the body absorbs and the concentration of lead-inair” (p. 8). Medical surveillance is required for those who have significant air lead exposures. If an employee’s BLL exceeds the action level (see below), the
The action levels are
a. BLL of 25 μg/dL in women of reproductive capacity.
b. BLL of 40 μg/dL in people 16 or 17 years old.
c. BLL of 50 μg/dL in any other employee.
The suspension levels are
a. BLL of 30 μg/dL or urinary lead adjusted for creatinine of 25 μg/g in women of reproductive capacity.
b. BLL of 50 μg/dL in young people not of reproductive capacity.
c. BLL of 60 μg/dL or urinary lead adjusted for creatinine of 110 μg/g in any other employee.
The guidance states that “some employees, excluding women of reproductive capacity, who have worked for many years in the lead industry, may have built up a high body burden of lead which could take a long time to fall below the suspension level of 60 μg/dL” (p. 70). They include employees who “a) have been employed on work which exposed the employee to lead for at least 20 years or b) are aged 40 years or more and may have been employed on work involving exposure to lead for at least 10 years” (p. 70). In those cases, “the employer may take some additional factors into account in deciding whether they should be taken off work involving exposure to lead” (p. 71), including the following:
1. Employees who meet either of the above conditions before 2002 may continue to work if BLLs are maintained under 80 μg/dL and ZPP levels are under 20 μg/g of hemoglobin, or ALAD levels are above 6 European units or aminolevulinic acid levels in urine (ALAU) are under 20 mg/g of creatinine.
2. Employees who meet either of the above conditions after 2002 may continue to work if BLLs remain under 70 μg/dL and ZPP levels are under 20 μg/g of hemoglobin, or ALAD levels are above 6 European units or ALAU levels are under 20 mg/g of creatinine.
It is important to note that the regulation prohibits employment of young persons and women in some tasks in lead smelting and refining and in lead-acid battery manufacturing.
The committee evaluated the exposure assessment methods used by the Department of Defense (DOD) for air sampling. This section describes the requirements
Occupational Safety and Health Administration Requirements
The OSHA lead standard (29 CFR 1910.1025) includes requirements for performing monitoring to measure employee exposures and to determine the sources of lead emissions. The standard requires that the monitoring be performed without regard to respirators, that is, the protective factor of any worn respirator cannot be used in the determination of the exposure of an employee (43 Fed. Reg. 52925 ).
The lead standard requires an initial assessment of lead exposures and requires that air sampling be performed or that air sampling performed in the previous 12 months be used to make the initial determination of employee exposure. The standard indicates that the air monitoring can be conducted on a sample of the exposed workers who are believed to have the highest exposures. Any additional monitoring is contingent on the findings of the initial assessment.
If the results of the initial assessment are negative (airborne concentrations were all below the action level of 30 μg/m3), no further monitoring is required. The results of the initial assessment need to be documented in writing. Further monitoring needs to be conducted only if a change in the process, controls, or personnel could result in an increased exposure to lead.
When the initial assessment indicates that personal exposures exceed the action level, additional monitoring is required. If measured exposures are between the action level and the PEL, monitoring must be performed every 6 months. If measured exposures are above the PEL, monitoring must be performed quarterly. Quarterly monitoring must continue until at least two sets of consecutive monitoring results are below the PEL.
Department of Defense Methods
DOD goes beyond the OSHA requirements of assessing the exposures of a sample of the exposed workers who have the highest lead exposures. It has incorporated the American Industrial Hygiene Association (AIHA®) Exposure Assessment Strategy. The strategy was first published in 1991 in Strategy for Occupational Exposure Assessment. The strategy was updated, and a second edition was published in 1998. The current third edition, A Strategy for Assessing and Managing Occupational Exposures, was published in 2006 (Bullock and Ignacio 2006).
The purpose of AIHA’s Exposure Assessment Strategy is to protect the health of workers by managing current and future risks with a program that is efficient and effective. The strategy uses a small number of samples (generally six to 10) to determine that worker exposures are acceptable or unacceptable or that more information is needed. The strategy involves placing workers into
similar exposure groups that perform the tasks or jobs in the same manner and therefore are expected to have similar exposures. Monitoring can be performed on the different similar-exposure groups so that acceptability can be judged. The AIHA Exposure Assessment Strategy requires personal exposures to generally be less than 10% of the PEL (or other standard being used) for a judgment of acceptability. The strategy potentially results in lower estimated exposures of workers (Bullock and Ignacio 2006).
Creation of the OSHA lead standard for general industry in the late 1970s was an important advance over occupational exposure limits that already existed. The OSHA standard is complex and includes more than the setting of a PEL or an action level. For example, air monitoring will not adequately capture lead exposures that occur via noninhalation routes, which can be important in firing ranges. In particular, ingestion of lead is of concern because of deposition of lead aerosols on hands during shooting or secondary hand contamination after contact with surfaces on which lead aerosols have collected or settled.
There are no data that directly link hand or surface contamination levels with specific BLLs, but studies have demonstrated that improved hygiene practices for both employees and the environment can lead to decreasing BLLs. Scott et al. (2012) found that although ventilation is an important method for controlling lead exposures, housekeeping can also have a substantial effect on lead contamination on surfaces in and around a shooting range. Even in ranges that have good ventilation and that use ammunition with lead-free primers, poor housekeeping or failing to decontaminate the range thoroughly before switching primers may adversely affect lead exposures. The Navy Environmental Health Center notes in its Indoor Firing Ranges Industrial Hygiene Technical Guide (NEHC 2002) that although there are no established limits for surface contamination in workplaces, OSHA (1993) has indicated in a compliance instruction for the construction industry (CPL 2-2.58) that an acceptable lead loading for nonlead work areas should be 200 μg/ft2. Appendix D of the Navy technical guide suggests clearance standards of 200 μg/ft2 for interior floors and horizontal surfaces and 800 μg/ft2 for exterior concrete (the latter is derived from an interim recommendation from the US Department of Housing and Urban Development).
It has been shown that high BLLs can result from lead ingestion during smoking and eating with lead-contaminated hands. Sato and Yano (2006) found that BLLs were substantially higher in battery-recycling employees whose hands showed lead contamination. In a longitudinal study of lead-battery employees in Taiwan, Chuang et al. (1999) found that smoking at work more than 3 days per week increased BLLs by 3.08 μg/dL compared with BLLs in those who had never smoked at work (p < 0.05). Although this is not statistically significant, mean BLLs were 1.32 μg/dL higher in employees who ate at work compared
Recent investigations have demonstrated that washing with soap and water is not an effective method for removing lead from skin. Sato and Yano (2006) demonstrated, using sodium sulfide to detect contamination by a change in skin color, that skin-color changes were more likely in lead-battery recycling employees who did not wash their hands or bathe beforehand or who had higher BLLs. Esswein et al. (2011) also developed a colorimetric method capable of detecting lead on skin and workplace surfaces. They demonstrated that hand decontamination, rather than washing, is required to ensure complete removal of lead. They found that a mixture of isostearoamidopropyl morpholine lactate and citric acid applied with a textured absorbent material was almost 100% effective in removing lead from skin. They suggest that the best method for preventing hand-to-mouth exposure may be skin decontamination and a colorimetric method to detect remaining contamination.
If DOD’s occupational exposure limit for lead is lowered, surface and skin decontamination are likely to play an even more important role in effective control of employee exposures than in the past. It will be important for an updated guideline to address the importance of decontamination in more detail and with greater precision. Where possible, quantitative levels of contamination should be included in guidelines rather than qualitative statements regarding the importance of housekeeping.
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