Jonathan Borak

Chemical warfare agents: II. nerve agents

Nerve agents are highly potent and rapidly acting organophosphorus compounds that irreversibly bind and inactive acetylcholinesterase. Only rarely have they been used in warfare, but their great lethality and the threat that they pose have encouraged production and stockpiling in large quantities. They differ in a number of important ways from common agricultural organophosphate insecticides. In light of recent threats of chemical warfare and the possibilities of chemical acts of terrorism, North American physicians should be knowledgeable of the effects of these agents and the care of exposure victims.

Agents of chemical warfare : sulfur mustard

Sulfur mustard is a chemical warfare agent of historical and current interest. Favored militarily because of its ability to incapacitate rather than its ability to kill, its use results in large numbers of casualties requiring prolonged, intensive care. In light of recent threats of chemical warfare and the possibilities of chemical acts of terrorism, North American physicians should be knowledgeable of its effects and the care of its victims.

Phosgene exposure : Mechanisms of injury and treatment strategies

Phosgene (carbonyl chloride, CAS 75–44–5) is a highly reactive gas of historical interest and current industrial importance. Phosgene has also proved to be a useful model for the study of those biochemical mechanisms that lead to permeability-type pulmonary edema (adult respiratory distress syndrome). In turn, the study of phosgene-induced adult respiratory distress syndrome has provided insights leading to revised treatment strategies for exposure victims. We summarized recent findings on the mechanisms of phosgene-induced pulmonary edema and their implications for victim management. In light of that research, we also provide a comprehensive approach to the management and treatment of phosgene exposure victims.

Comparison of NIOSH 5040 Method versus Aethalometer™ to Monitor Diesel Particulate in School Buses and at Work Sites

This study, undertaken initially to understand apparent differences between two recent reports of diesel particulate matter (DPM) inside school buses, involved side-by-side comparisons of two different methods for measuring ambient and occupational exposures to DPM. The NIOSH 5040 method yields time-weighted-average measurements of elemental carbon (EC) and organic carbon (OC), whereas the Aethalometer yields near-real time measures of carbonaceous particles (black carbon or BC) by optical absorption. The two methods were compared on three school buses and in three different work sites. Three side-by-side sampling configurations were used (open-faced filter with and without two different cyclones) in triplicate along with two or three Aethalometers. BC readings were correlated with results from open-faced cassettes, but there were statistically significant differences between the results of side-by-side Aethalometers. In addition, Aethalometer airflow rates were inaccurate, the instruments were sensitive to vibration, optical calibration could not be performed, and historically derived conversion factors to relate EC and BC were not appropriate. The Aethalometer could prove useful for monitoring of industrial work sites, but only after a method for external calibration and improvements in pump design and vibration isolation are developed.

Exposure of miners to diesel exhaust particulates in underground nonmetal mines.

A study was initiated to examine worker exposures in seven underground nonmetal mines and to examine the precision of the National Institute for Occupational Safety and Health (NIOSH) 5040 sampling and analytical method for diesel exhaust that has recently been adopted for compliance monitoring by the Mine Safety and Health Administration (MSHA). Approximately 1000 air samples using cyclones were taken on workers and in areas throughout the mines. Results indicated that worker exposures were consistently above the MSHA final limit of 160 micrograms/m3 (time-weighted average; TWA) for total carbon as determined by the NIOSH 5040 method and greater than the proposed American Conference of Governmental Industrial Hygienists TLV limit of 20 micrograms/m3 (TWA) for elemental carbon. A number of difficulties were documented when sampling for diesel exhaust using organic carbon: high and variable blank values from filters, a high variability (+/- 20%) from duplicate punches from the same sampling filter, a consistent positive interference (+26%) when open-faced monitors were sampled side-by-side with cyclones, poor correlation (r 2 = 0.38) to elemental carbon levels, and an interference from limestone that could not be adequately corrected by acid-washing of filters. The sampling and analytical precision (relative standard deviation) was approximately 11% for elemental carbon, 17% for organic carbon, and 11% for total carbon. An hypothesis is presented and supported with data that gaseous organic carbon constituents of diesel exhaust adsorb onto not only the submicron elemental carbon particles found in diesel exhaust, but also mining ore dusts. Such mining dusts are mostly nonrespirable and should not be considered equivalent to submicron diesel particulates in their potential for adverse pulmonary effects. It is recommended that size-selective sampling be employed, rather than open-faced monitoring, when using the NIOSH 5040 method.

The Beryllium Occupational Exposure Limit: Historical Origin and Current Inadequacy

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 and subsequently adopted by virtually all advisory and regulatory agencies, has persisted with only minor changes despite major advances in our understanding of berylliuminduced 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. The following year, the U.S. Department of Energy (DOE) published interim guidelines, with final regulations published in 1999, for a Beryllium Disease Prevention Program for workers at DOE sites, but DOE did not modify its OEL. Also in 1999, the American Conference of Governmental Industrial Hygienists (ACGIH) published a notice of intent to lower its threshold limit value (TLV) for beryllium, but no changes have been made. OSHA, in 2002, published a Request for Information as a first step toward setting a new beryllium PEL, 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.

Mortality Disparities in Appalachia Reassessment of Major Risk Factors

Objective: To determine the predictive value of coal mining and other risk factors for explaining disproportionately high mortality rates across Appalachia. Method: Mortality and covariate data were obtained from publicly available databases for 2000 to 2004. Analysis employed ordinary least square multiple linear regression with age-adjusted mortality as the dependent variable. Results: Age-adjusted all-cause mortality was independently related to Poverty Rate, Median Household Income, Percent High School Graduates, Rural–Urban Location, Obesity, Sex, and Race/Ethnicity, but not Unemployment Rate, Percent Uninsured, Percent College Graduates, Physician Supply, Smoking, Diabetes, or Coal Mining. Conclusions: Coal mining is not per se an independent risk factor for increased mortality in Appalachia. Nevertheless, our results underscore the substantial economic and cultural disadvantages that adversely impact health in Appalachia, especially in the coal-mining areas of Central Appalachia.

Use of Beryllium Lymphocyte Proliferation Testing for Screening of Asymptomatic Individuals: An Evidence-based Assessment

Objective: We reviewed published data describing use of beryllium lymphocyte proliferation testing (BeLPT) to determine the 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 scientific evidence to support the use of BeLPT for routine screening of asymptomatic individuals.

Cutaneous larva migrans in northern climates

Cutaneous larva migrans is a distinctive dermatitis caused by the filariform larvae of certain nematode parasites. Most often associated with tropical climates, it has increasingly been noted in nontropical settings. To familiarize northern clinicians with this condition, a case report is presented and its pathophysiology, diagnosis, and treatment are reviewed.

Biological versus ambient exposure monitoring of creosote facility workers.

Traditional methods for monitoring occupational creosote exposure have focused on inhalation. However, there is evidence that dermal exposure contributes importantly to total systemic dose, as measured by biological monitoring methods. This study was conducted to further characterize the relationships between inhalation and dermal exposures to creosote, and to compare traditional ambient exposure monitoring versus biological monitoring in 36 creosote-exposed wood treatment workers. Full-shift personal air samples were obtained, along with post-shift and next-day urine measurements for 1-hydroxypyrene. There was little or no correlation between airborne measures and urinary 1-hydroxypyrene (r2 = 0.05 to 0.35). More than 90% of 1-hydroxypyrene could be attributed to dermal exposure. These data indicate that traditional monitoring methods may be inappropriate for creosote workers, raising concerns about the adequacy of methods currently mandated by the Occupational Safety and Health Administration.