Employee Exposure Research Articles

Airborne Concentrations of Methylene Diphenyl Diisocyanate (MDI) in North American Wood Mills During the Manufacturing of Oriented Strand Board (OSB)

Air monitoring data were collected from industrial hygiene surveys over an 8-year period in oriented strand board (OSB) mills. Personal samples were taken to evaluate potential employee exposures to MDI. Area samples were taken to determine the effectiveness of control measures used in the mills to prevent fugitive emissions of wood dust, MDI, and MDI-coated wood dust from the OSB manufacturing process. Personal sampling results (578 samples covering 11 different job categories) ranged from 0.0002–0.524 mg/m3, with a GM = 0.001 and GSD = 3.71. Area sampling results (1657 samples covering 14 stationary locations in the mills) ranged from 0.0002–2.5 mg/m3, with a GM = 0.004 and GSD = 5.52. The statistical range of the data suggests high variability. While exposures to MDI above the established limits (0.051 mg/m3, 8-hour time-weighted average, 0.2 mg/m3, ceiling) can and do occur when engineering controls are not maintained and/or proper work practices and personal protective equipment are not followed/used for certain high exposure potential tasks, the data indicate that over 97% of the personal and 92% of the area sampling results are less than 0.051 mg/m3. Wipe testing was performed to determine the presence of removable, unreacted diisocyanates (NCO functional groups) from various surfaces. Positive results were found in about 13% of the wipe tests on surfaces confined to the blender, forming line, and hopper deck process areas.

Asbestos exposure and radiological abnormalities among maintenance and custodian workers in buildings with friable asbestos-containing materials.

Few studies have been carried out to evaluate the respiratory effects of asbestos exposure of custodian and maintenance workers. By a multicentre cross-sectional study, 277 custodian and maintenance employees working in buildings with friable asbestos-containing materials and 87 unexposed subjects were studied for radiological abnormalities by use of the International Labour Office (ILO) classification of radiographs of pneumoconiosis, in relation to parameters of asbestos exposure. The cumulative asbestos exposure index was generally low (fewer than 5 fibres/ml x years in 82.3% of exposed workers). On multivariate analysis, pleural thickening was significantly related to latency since onset of exposure to asbestos in exposed workers, after adjustment for age, body mass index and tobacco smoking. Asbestos exposure of custodian and maintenance employees in buildings with friable asbestos-containing materials might be associated with an excess of pleural thickening on chest X-rays.

Monkeypox in the United States

Between May 15 and June 20, 2003, 71 suspected cases of monkeypox were investigated and 37 individuals in the United States developed laboratory confirmed monkeypox. These were the first cases of human monkeypox ever documented in the United States or in the Western Hemisphere. The disease was transmitted from small animals imported from Africa to other animals, including prairie dogs sold as pets throughout the U.S. Midwest. Direct contact with the infected animals was the method of infection, and although human to human transmission was thought to have occurred, this was not confirmed by follow up testing. Because of the link with contact with a prairie dog, initial evaluation of the disease was focused toward diseases commonly associated with this animal (e.g., tularemia, plague). Laboratory findings at the Marshfield Clinic in Marshfield, Wisconsin pointed to the presence of an orthopox. The CDC confirmed monkeypox was the infecting orthopox agent. Occupational health nurses from the Marshfield Clinic had direct involvement in the identification and follow up of employees who had direct contact with the diagnosed patients. Programs, such as a respiratory protection program initiated and carried out by Clinic occupational health nurses, were used to prevent employee exposure for Clinic staff. One Clinic employee was thought to potentially have monkeypox because of her direct contact with one of the patients. Four Clinic employees were vaccinated with vaccinia vaccine as a result of their contact with patients or lab specimens. Quarantine of the potentially infected employee and her boyfriend uncovered issues that must be addressed if other infectious diseases requiring quarantine or isolation of individuals emerge or re-emerge. These include a system to compensate individuals in quarantine or isolation who do not have any other source of income. The issue of whether workers' compensation should cover an employee who is quarantined or isolated for a potential work related exposure to an infectious disease if no disease is actually diagnosed also needs to be explored. A better system of getting state or CDC laboratory results back to the local level, including the occupational health area of the generating facility, must be developed. This will be very important if diseases such as severe acute respiratory syndrome (SARS) or smallpox should re-emerge in the United States. Occupational health nurses are an integral part of any infectious disease process occurring in the United States. The identification of monkeypox in the United States shows that any planning to detect, prevent, and treat diseases with the potential to affect the employee population must include occupational health nurse involvement.

Ethics and choosing appropriate means to an end: problems with coal mine and nuclear workplace safety.

A common problem in ethics is that people often desire an end but fail to take the means necessary to achieve it. Employers and employees may desire the safety end mandated by performance standards for pollution control, but they may fail to employ the means, specification standards, necessary to achieve this end. This article argues that current (de jure) performance standards, for lowering employee exposures to ionizing radiation, fail to promote de facto worker welfare, in part because employers and employees do not follow the necessary means (practices known as specification standards) to achieve the end (performance standards) of workplace safety. To support this conclusion, the article argues that (1) safety requires attention to specification, as well as performance, standards; (2) coal-mine specification standards may fail to promote performance standards; (3) nuclear workplace standards may do the same; (4) choosing appropriate means to the end of safety requires attention to the ways uncertainties and variations in exposure may mask violations of standards; and (5) correcting regulatory inattention to differences between de jure and de facto is necessary for achievement of ethical goals for safety.

Cadmium Exposures at Three Nonferrous Foundries: An Unexpected Trace Source

Trace substances are often ignored as a potential source of significant occupational exposures. Trace substances include intermediates, byproducts, natural components, or a minor additive. An unexpected finding from a lead exposure assessment at a brass foundry was the identification of cadmium in one of the samples. Cadmium exposure was unexpected since it was not listed on the available documents (e.g., MSDS) and its presence was unknown to foundry representatives. Cadmium was found to be a trace component (maximum of 0.003%) in special high-grade (SHG) zinc added to molten brass or bronze alloys. Employees using as little as four pounds of SHG zinc containing 0.0004% cadmium had exposures that exceeded the Occupational Safety and Health Administration's 2.5 μg/m3 action level and 5 μg/m3 permissible exposure limit. Cadmium exposures at the three nonferrous foundries in this study were variable but, in general, metal pourers had the highest exposures (up to 7.2 μg/m3), followed by finishing workers (up to 1.9 μg/m3), and then furnace operators (up to 1.6 μg/m3). A pourer's exposure during a 3-min metal pouring cycle was 34.4 μg/m3. Air samples taken in the plume emitted after adding one pound (454 g) of zinc to the molten metal contained high cadmium levels (up to 3070 μg/m3) demonstrating zinc was the cadmium source. This study shows that the trace cadmium in SHG zinc can result in overexposures when used for brass and bronze alloying and trace components must be considered when evaluating potential employee exposures.

Four‐year follow‐up of smoke exposure, attitudes and smoking behaviour following enactment of Finland's national smoke‐free work‐place law

This study evaluated the possible impact of national smoke-free work-place legislation on employee exposure to environmental tobacco smoke (ETS), employee smoking habits and attitudes on work-place smoking regulations. Repeated cross-sectional questionnaire surveys and indoor air nicotine measurements were carried out before, and 1 and 3 years after the law had come into effect. Industrial, service sector and office work-places from the Helsinki metropolitan area, Finland. A total of 880, 940 and 659 employees (response rates 70%, 75% and 75%) in eight work-places selected from a register kept by the Uusimaa Regional Institute of Occupational Health to represent various sectors of public and private work-places. Reported exposure to ETS, smoking habits, attitudes on smoking at work and measurements of indoor air nicotine concentration. Employee exposure to ETS for at least 1 hour daily decreased steadily during the 4-year follow-up, from 51% in 1994 to 17% in 1995 and 12% in 1998. Respondents' daily smoking prevalence and tobacco consumption diminished 1 year after the enforcement of legislation from 30% to 25%, and remained at 25% in the last survey 3 years later. Long-term reduction in smoking was confined to men. Both smokers' and non-smokers' attitudes shifted gradually towards favouring a total ban on smoking at work. Median indoor airborne nicotine concentrations decreased from 0.9 micro g/m3 in 1994-95 to 0.1 micro g/m3 in 1995-96 and 1998. This is the first follow-up study on a nationally implemented smoke-free work-place law. We found that such legislation is associated with steadily reducing ETS exposure at work, particularly at work-places, where the voluntary smoking regulations have failed to reduce exposure. The implementation of the law also seemed to encourage smokers to accept a non-smoking work-place as the norm.

The basics of an exposure control plan

Prevention and control of employee injury and exposure begins with an organizational commitment to provide a safe work environment for the employees. An Exposure Control Plan (ECP) helps to ensure this safe environment, and is developed by an organization and administered to provide for the elimination and minimization of occupational exposure to blood-borne pathogens, which is one of the greatest areas of risk for the health care provider. The Occupational Safety and Health Administration (OSHA) standard 29 CFR 1010.1030, “Occupational Exposure to Bloodborne Pathogens,” outlines the requirements necessary to meet compliance as an institution. However, occupational exposure requirements have changed over the last few years and now incorporate practice advances regarding safety devices (ie, needleless and protected) and their use and implementation. Directives addressing the management of the employee who has been exposed to blood-borne pathogens have also been added. This article focuses on important elements in developing an institutional exposure control plan.

Workplace interventions for smoking cessation.

The workplace has potential as a setting through which large groups of people can be reached to encourage smoking cessation. To categorise workplace interventions for smoking cessation tested in controlled studies and to determine the extent to which they help workers to stop smoking or to reduce tobacco consumption. We searched the Tobacco Addiction Review Group trials register in November 2002, Medline (1966 - November 2002), EMBASE (1985 - November 2002) and PsycINFO (to November 2002). We searched abstracts from international conferences on tobacco and we checked the bibliographies of identified studies and reviews for additional references. We categorised interventions into two groups: a) Interventions aimed at the individual to promote smoking cessation and b) interventions aimed at the workplace as a whole. We applied different inclusion criteria for the different types of study. For interventions aimed at helping individuals to stop smoking, we included only randomised controlled trials allocating individuals, workplaces or companies to intervention or control conditions. For studies of smoking restrictions and bans in the workplace, we also included controlled trials with baseline and post-intervention outcomes and interrupted times series studies. Information relating to the characteristics and content of all kinds of interventions, participants, outcomes and methods of the study was abstracted by one reviewer and checked by two others. Because of heterogeneity in the design and content of the included studies, we did not attempt formal meta-analysis, and evaluated the studies using qualitative narrative synthesis. Workplace interventions aimed at helping individuals to stop smoking included nine studies of group therapy, three studies of individual counselling, eight studies of self-help materials and four studies of nicotine replacement therapy. The results were consistent with those found in other settings. Group programmes, individual counselling and nicotine replacement therapy increased cessation rates in comparison to no treatment or minimal intervention controls. Self-help materials were less effective. Workplace interventions aimed at the workforce as a whole included 13 studies of tobacco bans, two studies of social support, four studies of environmental support, four studies of incentives, six studies of comprehensive (multi-component) programmes and two studies of competitions and recruitment. Tobacco bans decreased cigarette consumption during the working day but their effect on total consumption was less certain. We failed to detect an increase in quit rates from adding social and environmental support to these programmes. There was a lack of evidence that comprehensive programmes reduced the prevalence of smoking. Competitions and incentives increased attempts to stop smoking, though there was less evidence that they increased the rate of actual quitting. We found 1. Strong evidence that interventions directed towards individual smokers increase the likelihood of quitting smoking. These include advice from a health professional, individual and group counselling and pharmacological treatment to overcome nicotine addiction. Self-help interventions are less effective. All these interventions are effective whether offered in the workplace or elsewhere. Although people taking up these interventions are more likely to stop, the absolute numbers who quit are low. 2. Limited evidence that participation in programmes can be increased by competitions and incentives organised by the employer. 3. Consistent evidence that workplace tobacco policies and bans can decrease cigarette consumption during the working day by smokers and exposure of non-smoking employees to environmental tobacco smoke at work, but conflicting evidence about whether they decrease prevalence of smoking or overall consumption of tobacco by smokers. 4. A lack of evidence that comprehensive approaches reduce the prevalence of smoking, despite the strong theoretical rationale for their use. 5. A lack of evidence about the cost-effectiveness of workplace programmes.

Air quality in an underground garage: computational and experimental investigation of ventilation effectiveness

The accumulation of contaminants that comes primarily from inside the building can constitute a potential health hazard in micro-environments where people spend most of their time indoors. The present paper refers to the numerical prediction of carbon monoxide (CO) concentration inside a typical garage in Athens urban area. Specifically, the study was concerned to investigate the indoor air quality and focuses on identifying the appropriate ventilation system as an attempt to improve air quality in workplace micro-environments. The model developed for the simulation of CO levels is used in conjunction with a general-purpose CFD code, PHOENICS that can provide detailed information on the CO concentration and velocity fields in a three-dimensional configuration. The transient variation of CO concentration was simulated under different scenarios of ventilation rates. Experimental measurements on the CO level inside the garage were performed using the portable, electrochemical CO monitor (Solomat’s MPM4100). From the continuous readings, instantaneous readings were stored every 15 s by the data log system. These data were used to verify the simulation results. Finally, the CO exposure of employees and garage’s users is assessed and compared with occupational limit value and recommended public health criteria. The results show that under the proper ventilation conditions the levels of CO concentration decrease and remain below the health based indoor air quality criteria.

From the Feds: Research, programs, and products

From the Feds: Research, programs, and products

Engineering controls for furniture strippers to meet the OSHA methylene chloride PEL.

This case study demonstrates how methylene chloride exposures during furniture stripping can be reduced to below the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) of 25 ppm (as an 8-hour time-weighted average). Five surveys were conducted at one facility; the first four resulted in employee exposure geometric means from 39 to 332 ppm. For the fifth survey local exhaust ventilation was used at the stripping tank and the rinsing area, which together exhausted 138 m3/min (4860 ft3/min). Additional controls included providing adequate make-up air, adding paraffin wax to the stripping solution, raising the level of the stripping solution in the tank, and discussing good work practices with the employee. The employees' methylene chloride exposures during the fifth survey resulted in a geometric mean of 5.6 ppm with a 95% upper confidence limit of 8.3 ppm, which was found to be significantly lower than the OSHA PEL and the OSHA action level of 12.5 ppm. The cost of the ventilation system was $8900.

Employee exposure to high-level radio frequency radiation.

Employee exposure to high-level radio frequency radiation.

Residential and Commercial Painters' Exposure to Lead during Surface Preparation

The California Painters Project was a 2-year intervention research project aimed at preventing lead poisoning among a group of residential and commercial painters in San Francisco, Calif. As part of this project 12 contractors invited project staff to conduct employee exposure monitoring. Twenty-five full-shift samples were collected, with 8-hr TWA results ranging from 0.8 to 550 microg/m3 (arithmetic mean: 57 microg/m3). Six of the 25 samples (24%) were above the Occupational Safety and Health Administration (OSHA) permissible exposure limit; all of these involved dry manual sanding or uncontrolled power sanding. Fifty-eight 30-minute task-specific samples also were collected. The arithmetic mean concentration results for heat gun use, wet sanding, and open flame burning were all under 10 microg/m3; the mean concentration for HEPA-exhausted power sanding was 33 microg/m3; dry manual scraping, 71 microg/m3; dry manual sanding, 420 microg/m3; and uncontrolled power sanding, 580 microg/m3. Analysis and modeling based on the 30-min results for dry manual sanding and uncontrolled power sanding indicate that painters' full-shift exposures often exceed 500 microg/m3 and the OSHA assigned level of protection for a half-mask air-purifying respirator. These results are cause for concern because both of these surface preparation methods are widely performed wearing half-mask respirators. The data show that HEPA-exhausted power sanding reduces paint dust exposure levels by approximately 80 to 90%. These tools should be more widely promoted as a safer alternative work method.

Employee Exposure to Chromium and Plasma Lipid Oxidation

Employee Exposure to Chromium and Plasma Lipid Oxidation

Employee Exposure to Chromium and Plasma Lipid Oxidation

Exposure to chromium increases free-radical species in the body, which has an adverse biologic effect. In view of evidence that the oxidation of low-density lipoproteins is important in the pathogenesis of atherosclerosis, the authors measured plasma lipid oxidation and antioxidant levels in 11 welders chronically exposed to chromium and compared them with levels in 15 matched controls. Exposure level was determined by urinalysis. Plasma lipid peroxidation and susceptibility to oxidation were determined by measuring generated thiobarbituric acid reactive substance (TBARS) and lipid peroxides. Total plasma antioxidant status and serum paraoxonase activity were also measured. The Kruskal-Wallis test was used to test for statistical significance. There was no significant difference between the groups with regard to lipid peroxidation, plasma lipid susceptibility to oxidation, total plasma antioxidant status, or serum paraoxonase. Three workers with urinary chromium levels over the biologic exposure index limit (> 10.0 microg/g creatinine) had higher plasma lipid peroxidation and lipid susceptibility to oxidation compared with the rest of the study group. The results suggest that welders exposed to chromium have increased plasma lipid oxidation. The small numbers of subjects and those with elevated urinary chromium limit the power of this preliminary study. Further studies of the association of chromium with plasma lipid oxidation are warranted.

Dust and Bioaerosols At a Biosolids Composting Facility

Workers at composting facilities are exposed to organic dusts and bioaerosols. The bioaerosols of major concern are Aspergillus fumigatus (A. fumigatus) and endotoxin. An evaluation of employee exposure to dust, endotoxin, and A. fumigatus spores was conducted in a totally enclosed biosolids composting facility that composts biosolids with sawdust. Total and respirable dust, endotoxin, and A. fumigatus were measured during several of the major composting activities. Periodic total dust levels exceeded the OSHA PEL standard for nonspecific dust. Endotoxin levels as high as 640 ng/m3 were recorded when piles were torn down. During mixing of biosolids and sawdust, A. fumigatus counts exceeded 6,000 CFU/m3. Based on the data obtained, several mitigation measures were implemented. Evaluation of the facility after the changes were made found that levels of total dust, endotoxin, and A. fumigatus were reduced by 90 percent.

Exposure to protein aeroallergens in egg processing facilities.

Proteinaceous materials in the air can be highly allergenic and result in a range of immunologically mediated respiratory effects, including asthma. We report on the largest evaluation of exposure to date of airborne egg protein concentrations in an egg breaking and processing plant that had cases of occupational asthma. Personal air samples for egg protein were analyzed in duplicate on each PTFE filter using two analytical methods: (1) a commercial assay for non-specific total protein, and (2) indirect competitive inhibition assay using an ELISA method to quantify specific egg protein components. The highest concentrations were found in the egg washing room (mean exposure 644 microg/m3) and breaking room (255 microg/m3), which were also the areas where the risk of being sensitized was the greatest. There was excellent quantitative agreement between the airborne concentrations of total protein and sum of the specific protein antigens (ovalbumin, ovomucoid, and lysozyme). The correlation coefficient of the log-transformed data from the two methods was 0.88 (p < 0.0001). Size-selective sampling also indicated that most of the aerosol was capable of reaching the small airways. The methods described can be utilized to evaluate employee exposure to egg proteins. Exposure documentation, coupled with recommended exposure reduction strategies, could facilitate prevention of future employee sensitization and allergic respiratory responses by identifying high-exposure jobs and evaluating control measures.

Time trends in exposure measurements from OSHA compliance inspections of the pulp and paper industry.

Time trends in employee exposures to the air contaminants measured by the Occupational Safety and Health Administration (OSHA) during compliance inspections of pulp and paper manufacturing facilities conducted between 1979 and 1997 were evaluated based on the measurement results stored in the OSHA Integrated Management Information System (IMIS) database. The IMIS database is among the largest sources of occupational exposure measurements available for occupational health research in the United States. The IMIS database contains the results of 3,568 personal time-weighted average (TWA) measurements for 171 air contaminants made at 524 establishments in Standard Industrial Classification (SIC) 26. An analysis of these measurements revealed an overall decrease in the total number of measurements made per year since 1991, and a decrease in the percentage of measurements by year that exceeded the OSHA permissible exposure limits (PELs). Linear regression analyses detected decreasing trends in the geometric mean concentrations by year for 33 of the 36 agents analyzed.

Occupational exposure to trihalomethanes in indoor swimming pools

The study evaluated occupational exposure to trihalomethanes (THMs) in indoor swimming pools. Thirty-two subjects, representing the whole workforce employed in the five public indoor swimming pools in the city of Modena (Northern Italy) were enrolled. Both environmental and biological monitoring of THMs exposure were performed. Environmental concentrations of THMs in different areas inside the swimming pools (at the poolside, in the reception area and in the engine-room) were measured as external exposure index, while individual exposure of swimming pool employees was estimated by THMs concentration in alveolar air. The levels of THMs observed in swimming pool water ranged from 17.8 to 70.8 μg/l; the mean levels of THMs in ambient air were 25.6±24.5 μg/m 3 in the engine room, 26.1±24.3 μg/m 3 in the reception area and 58.0±22.1 μg/m 3 at the poolside. Among THMs, only chloroform and bromodichloromethane were always measured in ambient air, while dibromochloromethane was detected in ambient air rarely and bromoform only once. Biological monitoring results showed a THMs mean value of 20.9±15.6 μg/m 3. Statistically significant differences were observed according to the main job activity: in pool attendants, THMs alveolar air were approximately double those observed in employees working in other areas of the swimming pools (25.1±16.5 μg/m 3 vs. 14.8±12.3 μg/m 3, P<0.01). THMs in alveolar air samples were significantly correlated with THMs concentrations in ambient air ( r=0.57; P<0.001). Indoor swimming pool employees are exposed to THMs at ambient air levels higher than the general population. The different environmental exposure inside the swimming pool can induce a different internal dose in exposed workers. The correlation found between ambient and alveolar air samples confirms that breath analysis is a good biological index of occupational exposure to these substances at low environmental levels.

Chemical health and safety challenges in a new era of enlightenment

Based on the experience of the past 30 years, some trends in chemical health and safety can be expected to continue during the new century. More health and safety information will be collected on specific chemicals; exposure hazard (threshold limit values and permissible exposure limits) and environmental impact databases will be expanded as new research is carried out in these areas. The mission of safety professionals will be to make the job safe for employees, including the elimination of excessive employee exposure to hazardous chemicals. Some ways to accomplish this include increased use of personal protective equipment and more thorough health and safety information on Material Safety Data Sheets. The objective is not to ban use of specific chemicals but to develop procedures to work safely with materials of interest. There will be increasing demands for products and processes involving chemicals and chemical reactions. Where will researchers obtain the necessary health and safety knowledge? Chemical health and safety information must become an integral part of the undergraduate and graduate chemistry curriculum.