Current Occupational Exposure Limit Research Articles

Cement Dust Exposure and Ventilatory Function Impairment: An Exposure–Response Study

We investigated cumulative total cement dust exposure and ventilatory function impairment at a Portland cement factory in Tanzania. All 126 production workers were exposed. The control group comprised all 88 maintenance workers and 32 randomly chosen office workers. Exposed workers had significantly lower forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), peak expiratory flow rate (PEF), FEV1/FVC, FVC%, FEV1% and PEF%, than controls adjusted for age, duration of employment, height, and pack-years. Cumulative total dust exposure was significantly associated with reduced FVC, forced expiratory volume in 1 second, and peak expiratory flow rate adjusted for age, height and pack-years. Cumulative total dust exposure more than 300 mg/m year versus lower than 100 mg/m years was significantly associated with increased risk of developing airflow limitation (odds ratio = 9.9). The current occupational exposure limit for total cement dust (10 mg/m) appears to be too high to prevent respiratory health effects among cement workers.

Six year observational cohort study of the effect of carbon disulphide on brain MRI in rayon manufacturing workers

Aims: To clarify whether the current occupational exposure limit (OEL) for carbon disulphide (CS2) is low enough to prevent the occurrence of adverse effects on the cerebrovascular system. Methods: A...

A six year follow up study of the subclinical effects of carbon disulphide exposure on the cardiovascular system

Aims: A six year prospective cohort study was conducted to clarify whether the current carbon disulphide (CS2) exposure level is low enough to prevent subclinical health impairment and/or to ameliorate...

Benzene exposure assessment for use of a mineral spirits-based degreaser.

This study examines benzene emissions from the use of a metal parts washer ("degreaser") supplied with a mineral spirits solvent containing either 9 or 58 ppm benzene. Air samples were obtained during a one-hour session of relatively vigorous parts cleaning activity using a degreaser station equipped with wet brush and sprayer attachments and a compressed air hose. Two methods were utilized to assess airborne benzene levels: U.S. EPA TO-14 (summa stainless steel canister) and NIOSH 1501 (charcoal tube). Overall, both methods provided similar results, excepting detection limit differences. The first simulation was performed with recycled solvent (9 ppm benzene in solvent) showing average one-hour airborne benzene levels < or =33 ppbv in the worker's breathing zone and directly above the parts cleaning tank. Average airborne benzene concentrations 18 inches away from the tank were below 2 ppbv during the 60-minute cleaning protocol. The second simulation with benzene-spiked recycled solvent (58 ppm benzene) showed airborne benzene levels averaging 500 ppbv measured over the 60-minute cleaning period in the worker's breathing zone and directly above the tank, while average concentrations 18 inches from the tank perimeter were 63 ppbv. The data indicate that average and peak exposures to airborne benzene were roughly proportional to the solvent benzene content, although the brief peak exposures exhibited greater variance probably related to aerosol generation associated with the use of the brush and/or spraying attachment. Under this selected upper bound exposure simulation, we found that cleaning parts using a recycled mineral spirits-based solvent in an open warehouse setting did not result in exposures in excess of the current occupational exposure limit of 0.5 ppm averaged over 8 hours for solvent benzene content between 9 and 58 ppm.

Surface area of respirable beryllium metal, oxide, and copper alloy aerosols and implications for assessment of exposure risk of chronic beryllium disease.

The continued occurrence of chronic beryllium disease (CBD) suggests the current occupational exposure limit of 2 microg beryllium per cubic meter of air does not adequately protect workers. This study examined the morphology and measured the particle surface area of aerodynamically size-separated powders and process-sampled particles of beryllium metal, beryllium oxide, and copper-beryllium alloy. The beryllium metal powder consisted of compact particles, whereas the beryllium oxide powder and particles were clusters of smaller primary particles. Specific surface area (SSA) results for all samples (N=30) varied by a factor of 37, from 0.56 +/- 0.07 m(2)/g (for the 0.4-0.7 microm size fraction of the process-sampled reduction furnace particles) to 20.8 +/- 0.4 m(2)/g (for the </=0.4 microm size fraction of the metal powder). Large relative differences in SSA were observed as a function of particle size for the powder of beryllium metal, from 4.0 +/- 0.01 m(2)/g (for the particle size fraction >6 microm) to 20.8 +/- 0.44 m(2)/g (for the particle size fraction </=0.4 microm). In contrast, little relative difference in SSA (<25%) was observed as a function of particle size for the beryllium oxide powder and particles collected from the screening operation. The SSA of beryllium metal powder decreases with increasing particle size, as expected for compact particles, and the SSA of the beryllium oxide powders and particles remains constant as a function of particle size, which might be expected for clustered particles. These associations illustrate how process-related factors can influence the morphology and SSA of beryllium materials. To avoid errors in predicting bioavailability of beryllium and the associated risks for CBD, the mechanisms of particle formation should be understood and the SSA of beryllium particles should be measured directly.

Lack of relationship between occupational exposure to carbon disulfide and endocrine dysfunction: a six-year cohort study of the Japanese rayon workers.

A six-year prospective cohort study was conducted to clarify whether the current carbon disulfide (CS2) exposure level is low enough to prevent subclinical health impairment and/or to ameliorate health effects due to previous high exposure. This paper describes the follow-up results, exposure assessment, and effects on the endocrine system. The study subjects were 432 male workers exposed to CS2 at one of the 11 rayon factories in Japan and 402 referent workers from the same factories, all of whom were examined in 1992-93. 251 CS2-exposed, 140 former-exposed and 359 referent workers participated in the follow-up survey (follow-up rate 89.9%) in 1998-99. Urinary 2-thiothiazolidine-4-carboxylic acid (TTCA) at the end of a shift as internal exposure index and the time-weighted average CS2 concentration as external exposure index were measured twice a year from 1992-1993. By using various blood indices, we evaluated effects on thyroid, hypophysis, and gonad function, as well as effects on glucose metabolism. Information on potential confounding factors, such as age, smoking and alcohol drinking, were collected and adjusted for. When the individual exposure level was represented by arithmetic mean for TTCA and CS2 concentration, geometric means (SD) of CS2 workers were 1.61 (1.91) mg/g.crea and 5.02 (1.84) ppm, respectively. There were no exposure-related differences in glucose metabolism or any of the endocrinological indices. No biologically significant effects of CS2 were found on endocrine function in Japanese rayon manufacturing workers when the average internal and external exposure levels were maintained below the current occupational exposure limit.

Scientific Criteria Used for the Development of Occupational Exposure Limits for Metals and Other Mining-Related Chemicals

The scientific approaches employed by selected internationally recognized organizations in developing occupational exposure limits (OELs) for metals and other mining-related chemicals were surveyed, and differences and commonalties were identified. The analysis identified an overriding need to increase transparency in current OEL documentation. OEL documentation should adhere to good risk characterization principles and should identify (1) the methodology used and scientific judgments made; (2) the data used as the basis for the OEL calculation; and (3) the uncertainties and overall confidence in the OEL derivation. At least within a single organization, a consistent approach should be used to derive OELs. Opportunities for harmonization of scientific criteria were noted, including (1) consideration of severity in identification of the point of departure; (2) definition of the minimum data set; (3) approaches for interspecies extrapolation; (4) identification of default uncertainty factors for developing OELs; and (5) approaches for consideration of speciation and essentiality of metals. Potential research approaches to provide the fundamental data needed to address each individual scientific criterion are described. Increased harmonization of scientific criteria will ultimately lead to OEL derivation approaches rooted in the best science and will facilitate greater pooling of resources among organizations that establish OELs and improved protection of worker health.

Airborne fiber exposure assessment of dry asbestos-containing gaskets and packings found in intact industrial and maritime fittings.

This study assessed airborne fiber exposures from intact asbestos-containing gaskets and packings while activities representative of historical work practices were performed. The study design eliminated analytical interferences while systematically capturing information related to activity variables. A series of gasket and packing activities was conducted according to traditional methods while sampling was performed to determine the 8-hour time-weighted average (TWA). The fittings used during this study were obtained intact from a decommissioned industrial power plant and U.S. Navy destroyers. The activities tested included flat blade scraping, hand wire brushing, power wire brushing, making gaskets with a ball-peen hammer, and stem packing removal and replacement. All activities were performed dry. Results for every area and personal sample showed the 8-hour TWAs were well below the current Occupational Safety and Health Administration permissible exposure limit of 0.1 f/cc. A database of more than 400 points was developed to analyze information from variable factors related to the tests. These factors included, for example, type of gasket, composition of the gasket, percentage of gasket adhering to a flange surface, gasket surface area, and minutes elapsed for removal. The results demonstrate a very low rate of fiber exposure from routine activities associated with asbestos-containing elastomeric gaskets and impregnated packing.

Methyl isobutyl ketone and methyl ethyl ketone in urine as biological markers of occupational exposure to these solvents at low levels.

To examine whether unmetabolized methyl isobutyl ketone in urine is a useful marker of low-level occupational exposure to this ketone solvent, as is the case for methyl ethyl ketone. The study was conducted in the second half of a working week. In total, 27 furniture-making workers (19 men and eight women) and 11 non-exposed controls (six men and five women) volunteered to participate in the study. Time-weighted average (TWA; 8-h) concentration of vapors of several solvents in air, including methyl isobutyl ketone (MIBK-A) and methyl ethyl ketone (MEK-A) was monitored by diffusive sampling. Urine samples collected at the end of the shift were subjected to head-space gas chromatography (GC) analysis for the unmetabolized solvents (i.e., MIBK-U and MEK-U). The relationship between the concentration of the solvent vapor and the corresponding solvent level in urine was examined by simple as well as multiple regression analysis. The exposures to MIBK and MEK were well below the current occupational exposure limit levels, but the maximum levels of exposure to toluene and ethylbenzene were around the corresponding exposure limit. The correlation of the TWA concentration of the solvent in air with the concentration of the corresponding solvent in the end-of-shift urine sample was significant both for MIBK and for MEK, and the correlation coefficient was larger for MIBK than for MEK. The slope in the exposure-excretion regression line was almost twice as steep for MEK than for MIBK, possibly due to the difference in water solubility. Approximately 0.12% of MIBK absorbed in the lungs will be excreted into urine, whereas the yield for MEK was somewhat higher (0.19%). MIBK in urine is a good marker of exposure to MIBK, as in the case of MEK in urine for MEK exposure.

Sulphur dioxide fume levels within theatre X-ray processing areas

A paper previously published by this journal demonstrated levels of sulphur dioxide (SO 2), above occupational exposure limits within satellite X-ray departments. These excess levels were linked to poorly maintained local exhaust ventilation (LEV) systems. The aim of the current study was to establish fume levels within all theatre X-ray processing areas in Dublin, Ireland and compare data with those of the previous investigation. Dräger diffusion tubes were placed at the illuminator and the entrance and exit processor trays within six theatre darkrooms in Dublin hospitals. Sulphur dioxide results were established, subjected to statistical analysis and compared with the occupational exposure limit of 2 parts per million (ppm). The resultant data indicated that all locations within the theatre darkrooms were substantially below occupational exposure limits and this was associated with proper maintenance of the LEVs in the departments of investigation. Significant inter-location differences were shown within most departments highlighting the importance of X-ray personnel demonstrating good working practices. The need for non-complacency amongst staff has been stressed as it has been shown that adverse health effects may exist amongst vulnerable individuals at a fraction of current occupational exposure limits and below all the levels presented in this study.

Inhalation exposures to acrylamide in biomedical laboratories.

This study evaluated airborne acrylamide exposures experienced by laboratory personnel using either crystalline or commercially available solutions of acrylamide to make polyacrylamide gels. Exposures were monitored for a short-term (15-min) sampling period, during the weighing of the crystalline acrylamide or the removal of the acrylamide solution from its original container, and a long-term period, during which a sample was collected for as long as the subject was potentially exposed to acrylamide. Mean air concentrations for the 15-min exposures were 7.20 +/- 5.64 micrograms/m3 and 5.81 +/- 4.53 micrograms/m3 for the users of crystalline and solution acrylamide, respectively, although this difference was not statistically significant (p > 0.05). Mean concentrations for the long-term exposures were 12.77 +/- 24.20 micrograms/m3 for workers employing crystalline acrylamide and 4.22 +/- 7.05 micrograms/m3 for personnel using acrylamide solutions. This difference was also not statistically significant. Although the results indicate that the research laboratory personnel were generally exposed to measurable concentrations of acrylamide, with several subjects exposed to elevated levels, the calculated 8-hour time-weighted average exposures were below current occupational exposure limits. However, because the neurotoxic effects of acrylamide are cumulative and it is a suspected carcinogen, all exposures should be kept as low as reasonably achievable.

Toluene diisocyanate concentration investigation among TDI-related factories in Taiwan and their relations to the type of industry.

To determine nationwide 2,4- and 2,6-toluene diisocyanates (TDI) concentrations among polyurethane (PU) resin, PU foam, and other TDI-related industries in Taiwan. The ratios of 2,4-/2,6-TDI and the noncarcinogenic risk among these three industries were also investigated. Personal and fixed-area monitoring of TDI concentrations as well as questionnaires were performed for 26 factories in Taiwan. The modified OHSA 42 method was applied in sampling and analysis. Noncarcinogenic hazard index was estimated for these three industries based on the average concentration measurements. Significant differences of TDI concentrations were found among the three industry categories. For personal monitoring, PU foam was found to have the highest TDI levels [18.6 (+/-33.6) and 22.1 (+/-42.3) ppb for 2,4- and 2,6-TDI], Others average [8.3 (+/-18.9) and 10.2 (+/-17.2) ppb], and PU resin lowest [2.0 (+/-3.5) and 0.7 (+/-1.2) ppb]. The estimated average hazard indices were found to be 310-3310. A substantial percentage of airborne TDI concentrations among in Taiwan industries exceeded current TDI occupational exposure limit, and significant difference of TDI levels were found among the three industry categories. The control remedy for the tasks of charging and foaming should be enforced with the highest priority. A separate 2,6-TDI exposure standard is warranted.

Exposures and their determinants in radiographic film processing.

Radiographers process X-ray films using developer and fixer solutions that contain chemicals known to cause or exacerbate asthma. In a study in British Columbia, Canada, radiographers' personal exposures to glutaraldehyde (a constituent of the developer chemistry), acetic acid (a constituent of the fixer chemistry), and sulfur dioxide (a byproduct of sulfites, present in both developer and fixer solutions) were measured. Average full-shift exposures to glutaraldehyde, acetic acid, and sulfur dioxide were 0.0009 mg/m3, 0.09 mg/m3, and 0.08 mg/m3, respectively, all more than one order of magnitude lower than current occupational exposure limits. Local exhaust ventilation of the processing machines and use of silver recovery units lowered exposures, whereas the number of films processed per machine and the time spent near the machines increased exposures. Personnel in clinic facilities had higher exposures than those in hospitals. Private clinics were less likely to have local exhaust ventilation and silver recovery units. Their radiographers spent more time in the processor areas and processed more films per machine. Although exposures were low compared with exposure standards, there are good reasons to continue practices to minimize or eliminate exposures: glutaraldehyde and hydroquinone (present in the developer) are sensitizers; the levels at which health effects occur are not yet clearly established, but appear to be lower than current standards; and health effects resulting from the mixture of chemicals are not understood. Developments in digital imaging technology are making available options that do not involve wet-processing of photographic film and therefore could eliminate the use of developer and fixer chemicals altogether.

Mercury vapour release from a dental aspirator.

To investigate the release of mercury vapour from a dental aspirator which vented its waste air through its base directly into the surgery environment. Mercury vapour in air concentrations were measured at the breathing zone of the dentist during continuous operation of the aspirator. Further series of mercury vapour measurements taken at the aspirator exhaust vent were carried out to determine the sources of mercury vapour from this particular device. At the dentist's breathing zone, mercury vapour concentrations of ten times the current occupational exposure limit of 25 micrograms/m3 were recorded after 20 minutes of continuous aspirator operation. A build up of amalgam contamination within the internal corrugated tubing of the aspirator was found to be the main source of mercury vapour emissions followed by particulate amalgam trapped within the vacuum motor. As the vacuum motor heated up with run time, mercury vapour emissions increased. It was found that the bacterial air exhaust filter (designed to clean the contaminated waste air entering the surgery) offered no protection to mercury vapour. In this case the filter trapped particulate amalgam which contributed to further mercury vapour contamination as high volume air was vented through it. It is not known how many dental aspirators are in use that vent their waste air directly into the surgery or if this aspirator is representative of others in existence. The safety of dental aspirating systems with regard to mercury vapour exposure requires further investigation.

The danger of mercury vapours from aspirators

Objective To investigate the release of mercury vapour from a dental aspirator which vented its waste air through its base directly into the surgery environment. Methodology Mercury vapour in air concentrations were measured at the breathing zone of the dentist during continuous operation of the aspirator. Further series of mercury vapour measurements taken at the aspirator exhaust vent were carried out to determine the sources of mercury vapour from this particular device. Results At the dentist's breathing zone, mercury vapour concentrations of ten times the current occupational exposure limit of 25 μg/m3 were recorded after 20 minutes of continuous aspirator operation. A build up of amalgam contamination within the internal corrugated tubing of the aspirator was found to be the main source of mercury vapour emissions followed by particulate amalgam trapped within the vacuum motor. As the vacuum motor heated up with run time, mercury vapour emissions increased. It was found that the bacterial air exhaust filter (designed to clean the contaminated waste air entering the surgery) offered no protection to mercury vapour. In this case the filter trapped particulate amalgam which contributed to further mercury vapour contamination as high volume air was vented through it. Conclusion It is not known how many dental aspirators are in use that vent their waste air directly into the surgery or if this aspirator is representative of others in existence. The safety of dental aspirating systems with regard to mercury vapour exposure requires further investigation.

Control of chemical risks during the treatment of soil contaminated with chlorophenol, creosote and copper-chrome-arsenic-wood preservatives.

Exposure to chemicals in polluted soil was studied during the remediation of four polluted sites. They are sawmill areas contaminated with chlorophenols and polychlorinated dibenzo-p-dioxins and furanes (PCDD/F), wood impregnating plants contaminated with polycyclic aromatic hydrocarbons (PAH) from creosote oil, old gas works area contaminated with PAH, and a wood impregnation plant contaminated with copper-chromium-arsenic (CCA) preservative. The exposure levels were determined by both air and biological monitoring. Air monitoring showed that the exposure levels were generally well below the current occupational exposure limits. The calculations indicated, however, that the lowest acceptable daily intake value recommended for PCDD/F by the U.S. Environmental Protection Agency was exceeded. Chlorophenol exposure was generally low. Exposure to volatile PAH was 0.038-0.884 mg/m(3) and that to particulate PAH was 0.004-0.183 mg/m(3). The biomonitoring results (urinary 1-pyrenol) suggested that some exposure occurs, probably through the contamination of hands or skin absorption. At the sites contaminated with CCA salts, no exposure limits were exceeded. The results generally suggest that the exposure of cleanup workers is generally below the current occupational exposure limits but that short-term high exposure cannot be excluded. There was also some indication of poor skin protection, which should be improved when soil contaminated with PAH and creosote oil is handled.

"Total" and respirable dust exposures in the U.S. carbon black manufacturing industry.

This article describes an industrywide exposure assessment study of "total" and respirable carbon black dust exposures among U.S. carbon black manufacturing workers conducted between 1993 and 1995. In addition to updating a 1979-1980 industrywide "total" dust study conducted among all major U.S. carbon black producers, this research was the first comprehensive evaluation of respirable dust exposures in the U.S. industry. A total of 2060 samples were collected (n = 1,004 "total," n = 1,056 respirable). The distributions of both dust fractions were lognormal with an overall "total" dust mean concentration, represented as the maximum variance unbiased estimator of 0.59 mg/m3 (range = 0.01-13.25 mg/m3), and an overall respirable dust mean concentration of 0.15 mg/m3 (range = 0.01-2.62 mg/m3). The fraction of "total" dust exposures greater than the current Occupational Safety and Health Administration permissible exposure limit of 3.5 mg/m3 was less than 3%. Material handling jobs experienced the highest "total" and respirable dust exposures, a finding consistent with the 1979-1980 study. The highest mean exposure for an individual job title was observed for product baggers/packers/sackers at 2.30 mg/m3 for "total" dust and 0.48 mg/m3 as respirable dust. Overall, mean "total" dust exposures had decreased significantly (up to 70%) for the majority of job classifications since the 1979-80 study. To evaluate the relationship between "total" and respirable dust fractions, 680 matched pairs of respirable and "total" samples were analyzed with a resulting mean ratio of 0.37 (respirable fraction to "total" dust). A log-transformed regression equation was obtained that provides a predictive relationship between "total" and respirable carbon black dust concentrations that may be applied to estimate the respirable fraction of historical "total" dust data collected under similar environmental and manufacturing conditions.

Misinterpretation and misuse of exposure limits.

Users of occupational exposure limits (OELs) often fail to distinguish between the complementary processes of risk assessment and exposure (risk) management. The former refers to those activities that lead to the selection of a reasonably protective exposure limit and often includes an analysis of exposure databases and an evaluation of group-based risk. The latter focuses on individual risk, and refers to those actions required of employers to ensure that each employee is unlikely to incur harm to health. This presentation focuses on how this failure to distinguish leads to misinterpretation and misuse of OELs. A typical OEL definition consists of at least three components: a concentration, an averaging time, and a target (usually the individual worker). OELs are occasionally improperly applied, resulting in a reduction of the expected level of protection. For example, sampling strategies proposed by the American Industrial Hygiene Association (AIHA) and Comité Européen de Normalisation (CEN) permit workers to be aggregated into exposure groups. Under certain circumstances this practice can leave some workers unevaluated and unprotected. Protection is also reduced when the averaging time is extended from a single shift to multiple shifts. Frequently, OELs are misinterpreted as upper limits to exposures averaged over weeks, months, or even years, rather than a single shift. Much of this confusion can be traced to the desire of some to reconcile research (epidemiology) sampling strategies with compliance sampling strategies. But the two have fundamentally different goals and objectives. Others are simply attracted to alternative OEL interpretations that permit frequent overexposures (i.e., measurements that exceed the OEL), thus making compliance easier. Given the current limitations of industrial hygiene and occupational epidemiology, and the general unwillingness of employers to routinely collect exposure data, OELs should continue to be defined as upper limits for single shift exposures. The current OEL model, which permits the use of proximate risk management goals to realize long-range objectives, should be retained. There are, however, valid reasons for augmenting this model to include criteria for evaluating compliance with long-range objectives. The augmented OEL model would be applicable to future new and revised OELs. The author suggests that OEL setting organizations consider harmonizing definitions and statistical interpretations for both existing and new OELs, thus minimizing future misinterpretation and misuse.

Possible metabolic interaction between hexane and other solvents co-exposed at sub-occupational exposure limit levels.

To investigate whether metabolic interactions exist between hexane (HEX) and other solvents when co-exposed at the levels below occupational exposure limits. Workers, 219 men in ten workshops in total, volunteered to participate in the study. They were occupationally exposed to mixtures of HEX and one or more of toluene (TOL), ethyl acetate (EA) and acetone (ACE). Time-weighted average intensity of vapor exposures was monitored by diffusive personal sampling. 'Free'- and 'total'-2,5-hexanedione (HD) levels in the end-of-shift urine samples were determined by gas chromatography (GC) before and after acid hydrolysis of urine, respectively, and expressed as observed (HDob) or after correction for creatinine concentration (HDcr) or urine specific gravity (HDsg). Possible interaction was examined by multiple regression analysis (MRA), taking either free- or total-HD as a dependent variable, and the four solvent concentrations as independent variables. In most cases, exposure intensity did not exceed the current occupational exposure limits even when additiveness was assumed. In addition that HEX was the most influential independent variable in all cases as expected, the MRA showed that, in cases of free-HD, ACE was also influential to HDob although weakly, but not to HDcr or HDsg. With regard to total-HD, ACE was weakly influential to HDob and HDsg, and EA also weakly to HDcr. The effect of ACE on free- or total-HD was not detected, however, when 22 men exposed only to HEX and ACE were subjected to the same analysis. Similarly, the effect of EA on total-HD was not observed among the remaining 197 men exposed to HEX, TOL and EA only. When the exposures were below occupational exposure limits, the free-HD levels in urine after HEX exposure will not be modified by co-exposures to TOL, EA or ACE.

Development of an eight-hour occupational exposure limit for beryllium.

This article recommends an 8-hour occupational exposure limit (OEL) for beryllium. It responds to growing concerns about the continuing incidence of chronic beryllium disease despite the long-standing OEL for beryllium: 2 micrograms of beryllium per cubic meter of air (microgram/m3), 8-hour time-weighted average (TWA). Current 8-hour TWA beryllium OELs are not based on chronic beryllium disease toxicology and an increasing number of studies report incidence of chronic beryllium disease at exposure levels apparently below 2 micrograms/m3. The experience of the beryllium-exposed population of Lorain, Ohio, in the late 1940s, and the ambient air regulatory standards derived from that event provide evidence that establishing a protective level is possible. These levels are used as the basis for a new recommended beryllium exposure standard. A correspondingly protective 8-hour TWA level of 0.1 microgram/m3 has been derived, which, for commonly encountered workplace conditions (in terms of geometric standard deviation and percent-compliance), should provide long-term mean exposure protection comparable to that received by the unaffected Lorain subpopulation and provided by the Environmental Protection Agency (EPA) ambient standard. It is concluded that an exposure limit of 0.1 microgram/m3 combined with exposure monitoring to assure a high rate of day-to-day compliance would provide better control of both long-term mean exposure levels and short-term levels than do current occupational exposure limits. The health data available, while certainly not conclusive, support further reductions in exposure levels to help minimize the incidence of chronic beryllium disease.