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Recent Peer-Reviewed Scientific Reports

Sirianni G, Hosgood H, Slade M, Borak J: Particle Size Distribution and Particle Size-Related Silica Content in Granite Quarry DustJournal of Occupational and Environmental Hygiene, (In Press)

Borak J, Hosgood HD: Seafood Arsenic: Implications for human risk assessmentRegulatory Toxicology and Pharmacology, 47:204-212, 2007.

Concerns about the adverse effects of chronic arsenic exposure have focused on contaminated drinking water and airborne workplace exposures; the risks of naturally occurring arsenic in foods have received less attention. About 90% of the arsenic in US diets comes from seafood, of which only a small proportion occurs in inorganic forms; the great majority consists of complex organic compounds that generally have been regarded as non-toxic. However, recent studies of seafood have documented formation of metabolites carcinogenic in some rodents. To calculate the risks of ingested seafood arsenic, therefore, it is necessary to identify the nature and quantity of arsenic species present and the metabolites formed by expected metabolic activities. We review the nature and quantities of the various arsenical compounds found in dietary seafood and discuss their metabolic processing and fate. Based on conservative dose estimates and the likelihood that arsenic’s carcinogenic mechanisms follow sub-linear dose–response curves, we estimate a margin of exposure of at least 103–104 between carcinogenic doses used in rodent studies and those expected after human consumption of large quantities of seafood.

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Borak J, Sirianni G: Studies of Self-Pollution in Diesel School Buses: Methodological IssuesJournal of Occupational and Environmental Hygiene 4: 660-668, 2007.

Considerable interest has focused on levels of exhaust emissions in the cabins of diesel-powered school buses and their possible adverse health effects. Significantly different policy and engineering issues would be raised if compelling evidence found that in-cabin contamination was due to self pollution from bus emissions, rather than ambient pollution, neighboring vehicles, and/or re-entrained road dust. We identified 19 reports from 11 studies that measured diesel exhaust particulate in the cabins of 58 school bus of various type. Studies were evaluated in light of their experimental design, their data quality, and their capacity to quantify self pollution. Only one study had a true experimental design, comparing the same buses with and without emission controls, while four others used intentional tracers to quantify tailpipe and/or crankcase emissions. Although definitive data are still lacking, these studies suggest that currently available control technologies can nearly eliminate particulate self-pollution inside diesel school buses.

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Rabinowitz PM, Slade MD, Galusha D, Dixon-Ernst C, Cullen MR: Trends in the prevalence of hearing loss among young adults entering an industrial workforce 1985-2004.  Ear and Hearing  27:369-75, 2006.

Objectives: Studies have suggested that hearing loss due to recreational noise exposure may be on the rise among adolescents and young adults. This study examines whether the hearing status of young US adults entering an industrial workforce has worsened over the past 20 yr. Design: The baseline audiograms of 2526 individuals ages 17 to 25 beginning employment at a multisite US corporation between 1985 and 2004 were analyzed to determine the yearly prevalence of hearing loss. Results: Approximately 16% of the young adults in the sample had high frequency hearing loss (defined as hearing thresholds greater than 15 dB in either ear at 3,4, or 6 kHz). In a linear regression model, this prevalence decreased over the 20-yr period (odds ratio (OR) 0.96, 95% confidence interval (CI): 0.94, 0.99). Almost 20% of subjects had audiometric “notches” consistent with noise exposure; this rate remained constant over the 20 yr, as did the prevalence (5%) of low frequency hearing loss. Conclusions: These results indicate that despite concern about widespread recreational noise exposures, the prevalence of hearing loss among a group of young US adults has not significantly increased over the past two decades.

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Borak J. The Beryllium Occupational Exposure Limit: Historical perspectives and current inadequacy. Journal of Occupational and Environmental Medicine  48:109-116, 2006.

This report considers the historical origin of the current beryllium occupational exposure limit (OEL) and the evidence that led most authorities to conclude that it was adequately protective against clinically evident chronic beryllium disease (CBD). Nearly 40 years later, during the late 1980s, it was shown that in addition to CBD, beryllium can cause asymptomatic sensitization and asymptomatic (“subclinical”) lung disease. It is now known that beryllium sensitization can progress to beryllium disease. Moreover, beryllium sensitization has been found in workers employed at facilities where exposures infrequently, if ever, exceeded the OEL. Historic beryllium exposure limits, which in their time seemed adequate to protect against clinically evident CBD, no longer seem sufficient. There is considerable concern that current occupational exposure limits (OEL) provide insufficient protection for beryllium-exposed workers.  The beryllium OEL, first proposed and  adopted by the U.S. Atomic Energy Commission (AEC) in 1949 1,2 and subsequently adopted by virtually all advisory and regulatory agencies, has persisted with only minor changes despite major  advances in our understanding of beryllium induced disease and important changes in the diagnostic approach used for beryllium-affected workers. Over the past decade, an increasing number of authorities have argued that the beryllium OEL should be lowered, but no changes have thus far been made. In 1996, Brush Wellman, the sole North American beryllium producer, expressed  uncertainty that the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) was adequately protective.3 The following year, the U.S. Department of Energy (DOE) published interim guidelines, 4 with final regulations published in 1999,5 for a Beryllium Disease Prevention Program for workers at DOE sites, but DOE did not modify its OEL. Also in 1999 American Conference of Governmental Industrial Hygienists (ACGIH) published a notice of intent to lower its threshold limit value (TLV) for beryllium, 6 but no changes have been made. OSHA, in 2002, published a Request for Information as a first step toward setting a new beryllium PEL, 7 but new values have yet to be proposed. The origins of the beryllium OEL and its persistence for more than 55 years provide interesting perspectives on historic and current practices of occupational medicine and industrial hygiene. Both its origin and persistence can be understood in light of the evolving knowledge about chronic beryllium disease (CBD) and the development of increasingly advanced diagnostic methods.

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Borak J, Woolf SH, Fields CA: Use of BeLPT for screening of asymptomatic individuals: An  evidence-based assessment Journal of Occupational and Environmental Medicine, Sep; 48: 937-47, 2006.

Objective:We reviewed published data describing use of beryllium lymphocyte proliferation testing (BeLPT) to determinethe appropriateness of BeLPT for screening asymptomatic individuals. Methods: Published studies were identified by computerized literature searches and hand searches of relevant bibliographies and cited references. Critical assessment of evidence focused on five elements essential to judging effectiveness of preventive services: 1) burden of suffering, 2) accuracy and reliability of screening tests, 3) effectiveness of early detection, 4) harms of screening, and 5) benefits outweighing harms. Results: Important gaps and deficiencies in the evidence were found. The prevalence of beryllium sensitization and chronic beryllium disease in asymptomatic individuals are unknown.The accuracy and reliability of BeLPT are uncertain. Marked intra and interlaboratory variability has been reported. The clinical benefits of early intervention have not been confirmed or quantified in asymptomatic individuals. Conclusions: There is currently insufficient scientificevidence to support the use of BeLPT for routine screening of asymptomatic individuals.

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Cohen H, White EM: Metalworking fluid mist occupational exposure limits: A discussion of alternative methods. Journal of Occupational and Environmental Hygiene 3: 501–507, 2006.

NIOSH published a recommended exposure limit (REL) for metalworking fluids (MWF) in 1998 that was designed to prevent respiratory disorders associated with these industrial lubricants. The REL of 0.4 mg/m3 (as a time-weighted average for up to 10 hours) was for the fraction of aerosol corresponding to deposition in the thoracic region of the lungs. This nonregulatory occupational exposure limit (OEL) corresponded to approximately 0.5 mg/m3 for total particulate mass. Although this REL was designed to prevent respiratory disorders from MWF exposures, NIOSH acknowledged that exposures below the REL may still result in occupational asthma and hypersensitivity pneumonitis—two of the most significant respiratory illnesses associated with MWF. In the 8 years since the publication of the NIOSH MWF REL, neither the Occupational Safety and Health  Administration (OSHA) nor the American Conference of Governmental Industrial Hygienists (ACGIH® ) has recommended an exposure limit for water-soluble MWF specifically, other than their previous exposure limits for mineral oil. An informal effort to benchmark companies involved in the manufacture of automobiles and automotive parts in North America indicated that most companies are using the NIOSH MWF REL as a guide for the purchase of new equipment. Furthermore, most companies have adopted a goal to limit exposures to below 1.0 mg/m3. We failed to find any company that has strictly enforced an OEL of 1.0 mg/m3 through the use of either administrative controls or personal protective equipment, when engineering controls failed to bring the exposures to below this limit. We also found that most companies have failed to implement specific medical surveillance programs for those employees exposed to MWF mist above 1.0 mg/m3. Organization Resources Counselors (ORC) published in 1999 (on their website) a “best practices” manual for maintaining MWF systems and reducing the likelihood of MWF-related illnesses. The emphasis of this approach was on control techniques, and there was no assignment of a specific OEL for MWF due to the wide variety of fluids that exist. The ORC did suggest that maintaining exposure levels to below 2.0 mg/m3 would assist in minimizing upper respiratory complaints associated with MWF. Although the ORC manual indicated that MWF vary in composition and no single OEL is likely to be appropriate for all such fluids, it adopted a very similar concept to control banding, placing all MWF operations into a single band using similar (if not identical) controls. OSHA, in lieu of adopting a 6B health standard for MWF, has also published a voluntary “best practices” manual on their website. Their document drew heavily from the work of ORC and also incorporated information from the 1998 NIOSH MWF criteria document. Industrial users of MWF need to have guidance, such as an OEL, to determine when either engineering, administrative controls, or personal protective equipment must be implemented to protect their employees. The purpose of this article is to explore various approaches that might be taken to result in a single or multiple limits for exposures to MWF and its components. Approaches such as control banding are discussed in terms of an alternative to the use of an OEL.

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Taiwo OA, Sircar KD, Slade MD, Cantley LF, Vegso SJ, Rabinowitz PM, Fiellin MG, Cullen MR: Incidence of asthma among aluminum workers. Journal of Occupational and Environmental Medicine  48:275-282, 2005.

Exposures to respiratory irritants encountered in aluminum smelters in Europe, Australia, and New Zealand have been suggested as the cause of “potroom asthma.” However, there remains disagreement in North America regarding the existence of this entity. This study was designed to assess whether asthma occurs excessively among potroom workers and if so, delineate dose–response relationships for possible causal risk factors. The asthma incidence ratio between potroom and nonpotroom workers after adjusting for smoking was 1.40. Although bivariate analyses showed a relationship between asthma incidence and exposure to total fluoride, gaseous fluoride, particulate fluoride, sulfur dioxide, and smoking, only the effects of gaseous fluoride (relative risk [RR] = 5.1) and smoking (RR = 7.7) remained significant in a multivariate model. Potroom asthma appears to occur at the studied U.S. aluminum smelters at doses within regulatory guidelines.

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Borak J: Adequacy of iodine nutrition in the United States. Connecticut Medicine, 69:73-77, 2005.

Concerns have been raised about the adequacy of iodine nutrition in the US despite recent NHANES III data indicating that iodine intake remains generally adequate.  Such concerns probably reflect misunderstanding of definitions of iodine deficiency.  We review current criteria for iodine deficiency, the reasons for variability of urine iodine determinations, and their relation to interpretations of NHANES data.  Although NHANES data indicate that iodine nutrition in the US is adequate, the possibility remains that those who adhere to restricted diets may have reduced intake of iodine.  Because of such possibilities, patients’ diets and use of dietary supplements should be explicitly considered as a part of routine medical care.

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 Borak J, Slade MD, Russi M: Risks of brain tumors in rubber workers: a meta-analysis. Journal of Occupational and Environmental Medicine 47: 294-298, 2005.

Concern that rubber industry workers suffer increased risks of brain tumor has persisted for over 40 years, despite numerous well-conducted studies that failed to detect excess brain tumors in appropriate cohorts.  To better understand this possible association, we performed a formal meta-analysis of brain tumor risk estimates reported in cohort studies of rubber and tire workers.  Twenty unique cohorts were identified that met a priori inclusion criteria.  Meta-analysis was performed using the General Variance-Based Method; the variance of risk estimates was calculated for each study using a chi-squared method. Homogeneity was tested by means of the Q statistic.  The meta-analysis determined an overall relative risk of 0.90 (95% CI: 0.79-1.02), consistent with a conclusion that risks of brain tumor are not increased as a result of occupational exposures in the rubber and tire industry. 

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Fields C, Dourson M, Borak J: Iodine-Deficient Vegetarians: A Hypothetical Perchlorate-Susceptible Population? Regulatory Toxicology and Pharmacology 42:37-46, 2005.

Recent risk assessments of environmental perchlorate have been subject to much debate.  A particular concern is whether appropriate susceptible subpopulations have been identified.  Iodine-deficient pregnant women, especially vegetarians, have been proposed as such a potential susceptible subpopulation, but there is no evidence of iodine deficiency in the US population and the adequacy of iodine nutrition has not been studied in US vegetarians.  To understand the possibility that US vegetarians might be iodine deficient, we reviewed the prevalence, demography, and life-style characteristics of US vegetarians as well as the world literature on iodine nutrition in vegetarians.  Our findings indicate that strict vegetarian and vegans, who comprise probably less that 0.1% of the US population, have higher education, higher incomes, and healthier lifestyles than the general population.  Field studies indicate that vegetarian diets need not lead to iodine deficiency and vegans may suffer excess iodine intake.  It remains uncertain whether there are iodine-deficient vegans or pregnant women in the US.  Of more general concern is whether the 10-fold default uncertainty factor is needed for intraspecies (i.e., within human) variability in order to protect such hypothetical susceptible subpopulations.

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Borak J, Sirianni G: Hormesis: Implications for cancer risk assessment. Dose Response  3;443-451, 2005.

Current guidelines for cancer risk assessment emphasize a toxicant’s “mode of action”, rather than its empirically derived dose-response relationship, for determining whether linear low-dose extrapolation is appropriate. Thus, for reasons of policy, demonstration of hormesis is generally insufficient to justify a non-linear approach, although it may provide important insights into the actions of toxicants. We evaluated dose-response characteristics of four carcinogens reported to have hormetic dose-response curves: cadmium chloride; ionizing radiation; PAHs; and, 2,3,7,8-TCDD. For each, the study that documented hormesis in one organ also provided evidence of non-hormetic dose-responses in other organs or non-hormetic responses for seemingly similar carcinogens in the same species and organs. Such inconsistency suggests toxicologic reasons that the finding of hormesis alone is not sufficient to justify use of non-linear low-dose extrapolations. Moreover, available data in those examples are not sufficient to know whether hormesis is a property of the toxicants, the target organ, or the exposed species. From the perspectives of cancer risk assessment, the greatest informational value of hormesis may be that it provokes mechanistic studies intended to explain why hormesis occurs.

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Enander R, Cohen H, Gute D, Brown L, Desmaris A, Missaghian R: Lead and Methylene Chloride Exposures Among Automotive Repair Technicians.  Journal of Occupational and Environmental Hygiene, 1: 119-125, 2004.

Potential exposures among repair technicians engaged in vehicle resurfacing operations prior to spray painting have not been thoroughly characterized.  Environmental and personal air monitoring conducted in the State of Rhode Island have shown that automotive repair technicians may be exposed to metal particulates in sanding dust and methylene chloride vapors during vehicle paint removal operations.  Hand wipe samples demonstrated that metals in sanding dust adhered to the hands of workers throughout the duration of the work day and were available for incidental ingestion from the handling of food/nonfood items and hand-to-mouth contact.  A blood lead (PbB) screening effort among 21 workers at 2 facilities showed that 4 non-/less-exposed workers had mean PbB levels at the U. S. geometric mean of 2.8 ug/dL, while 2 out of 9 (22%) dedicated vehicle repair technicians had PbB levels at or above 30 ug Pb/dL whole blood – the level for potential adverse reproductive effects.  Methylene chloride exposures were also found to exceed the Occupational Safety and Health Administrations (OSHA) 8-hr time-weighted average (TWA) action level and permissible exposure limit (PEL) in a limited number of samples (120 and 26 ppm, integrated work shift samples).  Our findings suggest that thousands of professional technicians and vocational high school students may be at increased risk of adverse reproductive and/or other systemic effects.

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