OSHA Permissible Exposure Limit Research Articles

AIR MEASUREMENTS OF DUSTS, CHEMICALS, AND FUMES

Estimates of exposure in the workplace or in indoor environments begin with the actual sampling and analysis of the airborne contaminant or rely on a reconstruction of past exposures in the workplace. Direct-reading portable field instruments are being used to supplement laboratory-based analytical methods. The lowering of the OSHA permissible exposure limits and the rise of indoor air pollution concerns indicate the need for more innovative methods for detecting lung irritants and pathogens.

Evaluation of worker exposure to benzene.

estimated 2-3 million workers are potentially exposed to benzene (ATSDR 1989). It is important to have cancer risk factors available for the evaluation of worker exposures in various settings. The risk factors for benzene published by the EPA are designed to evaluate general population exposure (not worker exposure) and do not include the results of recent studies. In this paper, risk factors are derived for the evaluation of worker cancer risk due to the inhalation and ingestion of benzene. These cancer risk factors are characterized by route, species, strain, sex, dose, dose rate/kg, and fraction of lifetime exposed. Such characterization facilitates the matching of a risk factor to any exposure situation. Example applications of the risk factors are presented. These examples concern OSHA's permissible exposure limit (PEL) for benzene, inhalation exposure at leaking underground gasoline storage tank sites (LUSTs), and ingestion of contaminated soil. MATERIALS AND METHODS Cancer risk factors are usually derived from experimental studies in units of excess risk/(mg/m 3) or excess risk/(mg/kg/day). Experimental studies can be animal or epidemiologic. In order to obtain a risk factor, it is first necessary to compute excess risk and equivalent human dose from an experimental study. Excess risk is the frequency of response in the exposed group corrected for the control group response. The equivalent human dose from an animal or epidemiology study is a function of the following variables: pharmacokinetics; body weight (or surface area); exposure concentration; daily Send reprint requests to W. Hallenbeck at the above address.

The health hazards posed by chromium-contaminated soils in residential and industrial areas: Conclusions of an expert panel

Between 1905 and 1971, over 2 million tons of residue from chromite ore processing was generated in Hudson County, New Jersey, of which substantial amounts were used as fill and tank diking. A panel of medical, toxicology, and risk assessment experts was convened in early 1990 to evaluate the potential health hazards posed by the resulting chromium contaminated soil. The Panel concluded that soils containing concentrations of 75 ppm hexavalent chromium [Cr(VI)] and 1000 ppm total chromium compounds (about 95% was trivalent chromium [Cr(III)]) did not pose a significant health hazard to nearby residents and workers. They also determined that exposure to chromium from Hudson County sites posed a negligible cancer hazard to residents. Using risk assessment methods, the Panel estimated that the plausible incremental cancer risk to individuals at residential sites would be substantially less than 1 in 1,000,000. The average measured levels of airborne Cr(VI) at typical industrial sites were more than 1000-fold lower than the current OSHA Permissible Exposure Limit (PEL). The maximum plausible increased cancer risk for an average worker at a dusty industrial site was estimated to be less than 1 in 100,000. The Panel also concluded that chromium-containing crystals, which have occasionally been found in Hudson County buildings, do not pose a significant hazard. However, they suggested that were the concentration to exceed 5000 ppm Cr(VI) in the crystals, site-specific health risk assessments would be conducted and remediation considered. The Panel evaluated the dermal hazard posed by chromium-contaminated soil and acknowledged that there is a small group of persons (approximately 0.1% of the United States population) who currently have a dermal sensitization to Cr(VI) primarily through occupational exposure. Based on published studies of human volunteers, the Panel concluded that a small percentage (less than 5%) of persons already sensitized may respond to Cr(VI) in solution at concentrations above 35 ppm. They decided that a much higher concentration in soil, perhaps 350 ppm Cr(VI), would be necessary to elicit dermatitis because only a fraction of the chromium in soil is soluble. The Panel concluded that it was highly unlikely (if not impossible) for a person to become dermally sensitized to Cr(VI) or Cr(III) at the soil concentrations found in most areas in Hudson County. The Panel was of the opinion that the 75 ppm total chromium [Cr(III) and Cr(VI)] cleanup requirement for Hudson County soils, which was established by the New Jersey Department of Environmental Protection (NJDEP), is unusually stringent and that much higher levels would still be protective of public health. Last, the Panel noted that although biological monitoring can be useful for evaluating persons exposed to relatively high concentrations of Cr(VI), the urine or blood sampling of persons living or working near these sites would probably not be beneficial until a more sensitive analytical method is available and/or until a very large control group is evaluated so that the background concentrations of chromium in biological fluids (and the variability) can be defined.

Cross-sectional neurotoxicology study of lead-exposed cohort.

Although the toxic effects of lead have been known for centuries, lead intoxication is still widespread in the United States. Without baseline tests of neuropsychological, neurobehavioral and neurophysiological testing it may be difficult to detect subtle changes in neurological function after lead exposure. This may be further confounded by partial chelation treatment and exposure to neurotoxic mixtures or inability to quantitate alcohol consumption. We undertook a cross-sectional study to address these problems in 24 exposed and 29 control subjects in a plant that manufactured electrical components using fritted leaded glass to coat capacitors and transistors. Potentially exposed workers had blood lead levels ranging between 3 micrograms/dL to 135 micrograms/dL. Industrial hygiene monitoring revealed the plant's air lead levels ranged from 61 micrograms/m3 to 1,700 micrograms/m3 in excess of OSHA permissible exposure limits of 40 micrograms/m3/10 hr day. Using a specially designed battery of neurophysiological, neurobehavioral and neuropsychological screening tests, we demonstrated a significant difference from controls in measures of psychomotor speed, motor strength and verbal memory. Although limited by the cross-sectional design, these findings support the hypothesis that the battery of neurophysiological, neuropsychological and neurobehavioral tests can detect a significant inter-group differences between lead-exposed and control subjects.

Industrial Hygiene and Control Technology Assessment of Ion Implantation Operations

Ion implantation is a process used to create the functional units (pn junctions) of integrated circuits, photovoltaic (solar) cells and other semiconductor devices. During the process, ions of an impurity or a "dopant" material are created, accelerated and imbedded in wafers of silicon. Workers responsible for implantation equipment are believed to be at risk from exposure to both chemical (dopant compounds) and physical (ionizing radiation) agents. In an effort to characterize the chemical exposures, monitoring for chemical hazards was conducted near eleven ion implanters at three integrated circuit facilities, while ionizing radiation was monitored near four of these units at two of the facilities. The workplace monitoring suggests that ion implantation operators routinely are exposed to low-level concentrations of dopants. Although the exact nature of dopant compounds released to the work environment was not determined, area and personal samples taken during normal operating activities found concentrations of arsenic, boron and phosphorous below OSHA Permissible Exposure Limits (PELs) for related compounds; area samples collected during implanter maintenance activities suggest that a potential exists for more serious exposures. The results of badge dosimetry monitoring for ionizing radiation indicate that serious exposures are unlikely to occur while engineering controls remain intact. All emissions were detected at levels unlikely to result in exposures above the OSHA standard for the whole body (1.25 rems per calendar quarter). The success of existing controls in preventing worker exposures is discussed. Particular emphasis is given to the differential exposures likely to be experienced by operators and maintenance personnel.(ABSTRACT TRUNCATED AT 250 WORDS)

The quality of respirator programs: an analysis from OSHA compliance data.

The quality of respirator programs in typical workplaces was investigated by analyzing the history of compliance with OSHA Standard 29 CFR 1910.134 (respiratory protection). Analysis was focused on the approximately 47 000 health inspections conducted in the manufacturing industries [Standard Industrial Classification (SIC) Codes 2000-3999] in the period of October 1, 1976 to September 30, 1982. During this period, approximately 27% of inspections in which respirator programs were reviewed resulted in a citation for a specific program deficiency. Of inspected worksites in which respirators were in use to provide protection from concentrations of air contaminants in excess of OSHA Permissible Exposure Limits, 56% had deficiencies in at least one program area. Since the violations were of the type that have been shown to lower the level of protection provided by respirators, many workers may have been exposed to inhalation hazards as the result of ineffective respirator programs.

A passive sampling device for determining formaldehyde in indoor air

A passive sampling device based on the principle of diffusion has been developed for the determination of formaldehyde in ambient air. The sampler consists of a capped glass tube (with approximate dimensions of 2.4 × 9 cm) containing a glass-fiber filter treated with NaHSO 3. In the field, the device collects a sample by being uncapped for a specified sampling time. After being recapped and returned to the laboratory, the filter is analyzed by the chromotropic acid (CTA) method. Laboratory validation studies were conducted by exposing the sampling devices for 1 week to dry formaldehyde gas generated by passing trioxane vapor over an acid catalyst bed. In these tests, formaldehyde concentrations ranged from 0.05 to 0.80 mL/m 3. Reproducibility was excellent, with relative standard deviations averaging 5.4% for five constant concentrations. The lower detection limit was determined to be 3.6 mL/m 3 h. In an occupational environment an 8-h sample would be sufficient to detect compliance with the OSHA permissible exposure limit of 3 mL/m 3; in a residential environment a 1-week sample would allow detection of 0.025 mL/m 3 for indoor air quality audits.

Ferric chloride leach-electrolysis process for production of lead.

The U.S. Department of the Interior, Bureau of Mines, under a cost-sharing, cooperative research agreement with lead producers, is studying a process to eliminate sulfur oxide generation and to minimize lead emission in the production of lead. The new process consists of leaching lead sulfide concentrate with a ferric chloride-sodium chloride solution to produce lead chloride, and fused-salt electrolysis of lead chloride to produce lead metal and chlorine. The chlorine is used to regenerate ferric chloride in the leach solution. The study is being conducted in a process investigation unit which treats 750 lb of concentrate a day. This paper discusses the results of operation of the process investigation unit, data on lead monitoring, and the precautions employed to control lead levels in the workplace atmosphere. The monitoring data for the initial phase of the investigation show lead levels well within OSHA permissible exposure limits. Continued development is necessary before the process can be considered for implementation.