FRANK MIRER, PhD, CIH, is a professor in the CUNY School of Public Health in New York. He can be reached at (212) 396-7782 or firstname.lastname@example.org. Editor’s note: Frank Mirer’s Synergist contributions previously appeared in our Insight section. This month marks Mirer’s first appearance in the Columns section. His “Risky Business” column will continue to focus on regulations, public policy, and the science of industrial hygiene.
Getting the Lead Out Catching Up to New Science
BY FRANK MIRER
Lead exemplifies the advance of authoritative conclusions about workplace hazards, especially potency, against the backdrop of no advance in regulatory protections. For lead, the advances in interpretation come from population studies rather than the pre-1975 occupational studies that are the basis of the OSHA regulation. The OSHA lead-in-air (LIA) limit, 50 µg/m3, is intended to limit employees’ body burden of lead, as indicated by lead in blood (LIB), to less than 50 µg/dl (100 grams of blood). The standard was promulgated in 1978, and was constrained by feasibility of engineering controls in the most difficult industry sector, smelters, as well as the health data of the time. The 2012 authoritative review by the National Toxicology Program notes “sufficient” evidence for decreased glomerular filtration rate; the association of maternal lead-blood levels with reduced fetal growth at < 5 µg/dl in adults; and increased blood pressure, risk of hypertension, and incidence of essential tremor at <10 µg/dl. (This exhaustive collection of data, which was subjected to extensive peer review, noted other effects with “limited” evidence.) The issue for IHs should be adjusting the LIA limit to the more protective LIB criteria. HISTORY Lead came up on the OSHA regulatory agenda during the golden age of rulemaking in 1978. The Steelworkers led the hearings for the labor movement. I testified before OSHA on behalf of the United Auto Workers in April 1977, and organized panels of union leaders and rank-and-file workers to testify as well. The Teamsters were also very important. When the lead standard was issued, industry filed a lawsuit against OSHA. In 1980 the DC Court of Appeals upheld the standard, finding it feasible in industries with the highest exposures (smelters, battery plants). The Court also upheld the revolutionary medical removal protection-multiple physician review (MRP-MPR) provisions. With the change in presidential administration in 1981, the Reagan OSHA joined industry in appealing against the standard, but this was rejected by the courts. The 1978 lead standard omitted construction. In response to a union lawsuit, OSHA agreed to move forward in construction but failed to act until Congress passed the Housing and Community Development Act of 1992 requiring a construction lead standard. The standard specified detailed work practices. The adverse effects of lead on reproduction and development, noted in the OSHA record, also spawned a surge in “fetal protection” policies, in which managements recently forced by the Equal Employment Opportunity Commission to hire women into well-paying blue collar jobs attempted to “protect” women from lead by terminating them, while leaving men to be exposed despite evidence for adverse developmental results from paternal exposure. In April 1975, Bunker Hill Smelter in Idaho required women workers who wanted to retain higher-paying jobs to be sterilized. The fetal protection issue spawned multiple lawsuits, finally resolved in 1991 when the Supreme Court reversed lower courts and ruled fetal protection policies illegal in UAW v. Johnson Controls.
Despite its shortcomings, the OSHA lead standard caused nearly revolutionary improvements for workers in lead industries.
Despite its shortcomings, the OSHA lead standard caused nearly revolutionary improvements for workers in lead industries. Once OSHA started rulemaking, it was all downhill to a protective standard that survived legal challenge by industry. Partly as a result, the industry strategy since has been to prevent OSHA from starting rulemaking on chemicals. BASIS FOR THE CURRENT OSHA STANDARDS The explanation of the 1978 standard shows that OSHA sought to identify a body burden of lead—as indicated by LIB measurements—associated with adverse health effects, then sought to identify an LIA level that would keep the body burden below the LIB level. Workers whose LIB reached a dangerous range, or who suffered signs of illness, would be pulled out of exposure according to MRP-MPR, to be returned when the level decreased. This yo-yo process was standard industry practice at the time. The preamble to the lead standard states that LIB >40 µg/dl was associated with a risk, but the MRP-MPR provisions only require removal with a three-test moving average >50 µg/dl, with return permitted when the level got below 40 µg/dl. Today these values would be considered high, if not alarming, but in the middle 1970s about 70 percent of LIB measurements among battery plant workers (I had the data) were >40 µg/dl. Next, OSHA had to identify an LIA limit consistent with the LIB goals. There were no robust direct observations (such as multiple air samples, with attendant variability, and blood samples on a representative number of workers). So a pharmacokinetic model was used, which projected that 30 percent of workers would suffer LIB results >40 µg/dl, 6 percent between 40–50, and 1 percent >60 at an LIA of 50 µg/m3. The explanation provided in the lead standard preamble states, “While OSHA agrees with the goal that blood lead levels should be kept below 50 µg/100 g where possible, and in fact preferably below 40 µg/100 g, the levels required to achieve the latter value are clearly infeasible in the foreseeable future.” The OSHA LIA limit of 50 µg/m3 (total dust) is still as strict as any in the world. But we are now beyond OSHA’s “foreseeable future,” and it’s time to reassess both health and feasibility. Generally, lead exposure has been radically reduced. The median LIB result for adults in the U.S. is about 1 µg/dl; in 1976, my LIB was 25 µg/dl (confirmed by the Chrysler IH lab) with no occupational lead exposure beyond some battery-plant walkthroughs. EPA has reduced the National Ambient Air Quality Standard for lead to 0.15 µg/m3 (from 1.5 µg/m3). California EPA recently reassessed LIA-LIB associations; their model predicts a median LIB of 20 µg/dl at an LIA of 18 µg/m3, with 5 percent of results >43 µg/dl. An estimate based on surface contamination was shelved. For a median LIB of 10 µg/dl, the LIA would be 7 µg/m3. For IHs overseeing a lead removal project, the goal should be to apply all feasible controls to operations in the purgatory between the 1978 standard and current health criteria. First, we have to understand (and resist) complexity in exposure assessment. “Inhalable” (<50 µ) particle measurements are as much as three times “total” (closed-face cassette) results side by side, so there’s invisible exposure going to the gut, while only a fraction of the total is going to the alveolar surface. We could also invoke the chemical state of lead to suggest more complex and expensive assessments, and looser evaluation criteria (which have evolved for lead oxide dust and fume). Second, any LIB >10 µg/dl in a group of similarly exposed workers should trigger assessment of sources of exposure for the whole group, not just the worker with the elevation. Variation in absorption and storage means that the LIB is an imperfect measure of body burden. Precautions should be taken for all similarly exposed workers. Third, protections should be based on exposure. We should not be yo-yoing workers in and out based on their LIB. Regarding a possible PEL update, a question of priority still remains. Should OSHA attempt to improve a deficient but semi-modern standard, or focus on substances for which exposure limits are mired in the deeper past?
- California EPA: “Estimating Workplace Air and Worker Blood Lead Concentration using an Updated Physiologically-based Pharmacokinetic (PBPK) Model” (PDF, Oct. 2013).
- Cornell University Law School: UAW v. Johnson Controls (March 1991).
- OSHA: Regulations (Preambles to Final Rules).
- National Toxicology Program: “NTP Monograph: Health Effects of Low-level Lead” (PDF, June 2012).
Opposition to the use of Agent Orange in Vietnam was part of my motivation to move from chemistry to toxicology, and the insecticide parathion was part of my post-doctoral project. And I claim expertise (or at least experience) in this process by serving on two IARC working groups, and on National Toxicology Program (NTP) peer review groups for bioassay reports, the criteria for evaluating those bioassay reports, and the Report on Carcinogens (ROC).
- Frank Mirer
IARC Monographs Volumes 112 and 113 address insecticides and herbicides. They classify lindane as known to be carcinogenic to humans (Group 1); DDT, malathion, and diazinphos as probably carcinogenic (Group 2A); and 2,4-D, tetrachlorvinphos and parathion as possibly carcinogenic (Group 2B). Although few IHs work in agriculture, we are likely to get questions about pesticide use in homes and, regarding glyphosate, on our lawns.
- Frank Mirer