Pollution prevention and the work environment: the Massachusetts experience.

In 1989, Massachusetts enacted the Toxics Use Reduction Act. The Act defined toxics use reduction, also referred to as pollution prevention, as "in-plant changes in production processes or raw materials that reduce, avoid, or eliminate the use of toxic or hazardous substances or generation of hazardous by-product per unit of product ... without shifting risks between workers, consumers or parts of the environment." The investigators sought to understand to what extent worker health and safety concerns have been integrated into toxics use reduction activities and how these activities have affected the work environment. The authors reviewed 35 published case studies of toxics use reduction in Massachusetts companies and interviewed key personnel including the staff of the Massachusetts Office of Technical Assistance for Toxics Use Reduction. Overall, between 1990 and 1997, Massachusetts companies decreased their use of toxic chemicals by 24 percent and decreased their volume of toxic by-product by 41 percent. In almost 50 percent of the cases analyzed, improved worker health and safety was cited as a benefit of the toxic use reduction projects. Solvents were eliminated or reduced in 63 percent of the cases. Forty-six percent of the companies profiled introduced water-based chemicals in place of more volatile ones; and acids and caustics were reduced or eliminated in 20 percent of the cases. The investigators concluded that toxics use reduction activities have resulted in improvements to the work environment, but that such improvements were rarely a direct concern of these efforts, thus creating the potential for new negative worker health and safety impacts and missed opportunities to coordinate environmental and worker health and safety improvements. The authors recommend that technical assistance agencies and companies better integrate worker health and safety issues and pollution prevention activities.

Implications of different fiber measures for epidemiologic studies of man-made vitreous fibers.

BACKGROUND: Several researchers have proposed fiber size ranges representing hypotheses about the biological activity of fibers. Each of these indices has a biologically plausible rationale, yet they propose different fiber dimensions. METHODS: Four biologically based and one standard fiber analytic method index, the NIOSH 7400 method with B rules, were evaluated in air monitoring data collected in a variety of fiber glass (FG) manufacturing settings to determine their impact on an assessment of fiber exposure for an epidemiologic study of the risk of respiratory cancer among FG production workers. RESULTS: All indices varied considerably within and among the range of fiber size distributions sampled in the FG factories. CONCLUSIONS: The asymptotic relative efficiencies (R(2)) calculated among the five indices indicate a potentially important loss of power from the use of the standard method index, if one of the biologically based indices is more closely related to the disease outcome in an epidemiologic study.

Use of a job-exposure matrix to assess occupational exposures in relation to birth defects.

Accurate exposure assessment remains a challenge in occupational epidemiology. We evaluated one approach, use of a job-exposure matrix (JEM), by applying the National Institute for Occupational Safety and Health (NIOSH) JEM to a large case-control birth defects study that included parental occupation information. We investigated the JEM exposure predictions in several ways and found that for a substantial proportion of the parents in the birth defects study, the JEM yielded either no exposure data or nonsense predictions. Among exposure predictions that were plausible, most were of low probability. The high probability exposure predictions were statistically unstable, and neither low nor high probability exposure predictions were reliable. There was considerable discrepancy between the JEM predictions and expert assessments for five exposures of interest. Application of the NIOSH JEM to the birth defects study database (and probably other databases as well) does not provide a useful means of assessing occupational exposures.

Engineering controls as an intervention to reduce worker exposure.

The implementation of controls to reduce worker exposure should be considered the ultimate goal of any successful industrial hygiene program. The industrial hygiene literature has consistently described a hierarchy of controls, consisting first of the engineering controls (substitution, isolation, ventilation), and followed by administrative controls (personal protective equipment, worker education, scheduling etc.). Recently, exhaust ventilation has been the most popular form of engineering control technology for controlling exposure to airborne contaminants. The use of ventilation to control exposures is not without its problems, however, and many of these problems potentially are more severe in smaller companies. This paper proposes a new emphasis on the first control in the hierarchy, substitution. Historically, substitution has meant the substitution of a hazardous chemical or process by one that is less so. This definition is too restrictive; because of this, it is proposed instead to use the term process change, defined as the use of any process modifications that serve to reduce worker exposure. The advantages and disadvantages of the process change approach are discussed and are illustrated with case studies.

Comparisons between magnetic field exposure indices in an automobile transmission plant.

Personal monitoring of extremely low frequency magnetic fields was conducted at a large automatic transmission plant for a case-control study of primary brain cancer. Current workers were selected to represent the jobs most commonly held by study subjects. Several exposure indices, corresponding to different plausible biological mechanisms, were computed for each of 81 workers who wore the monitoring instrument for one-half shift. Average exposures covered a range from 0.16 to 46 mG; median exposure was 1.3 mG. Nonparametric correlations were estimated to learn whether all of these indices rise and fall together. Results were mixed, in that indices sensitive to high values showed correlations above 0.7, but other correlations were between 0.4 and 0.6. Different indices may thus identify different groups as "highly" exposed. The authors also tested whether indices based on the fraction of time spent above hypothesized thresholds were accurately predicted by a lognormal model. For 47% of the workers, the observed indices significantly exceeded those predicted by such a model, suggesting that lognormality is not a good model for distributions of individuals' short-term exposures.

An empirical model for estimating the collection efficiency of dust-mist respirators.

This paper compares experimental measurements of filter performance with predictions of aerosol collection by dust-mist respirators using the single fibre efficiency model and an empirical model developed by the authors. The former, a theoretically-based semi-empirical model, indicates that mechanical phenomena such as impaction, interception and diffusion are responsible for only a fraction of the collection efficiency of dust-mist respirators, i.e. 30-70% depending on particle size. The difference between these relatively low predicted efficiencies and experimentally observed values, which were greater than 95%, can be attributed to electrostatic forces. Because it was not possible to determine filter fibre charge the single fibre efficiency model could not be used to predict electrostatic collection. An empirical model developed from experimental data with monodisperse latex aerosols was used to predict silica and asbestos collection. The empirical model adequately described silica collection, but predicted much higher asbestos penetration than was observed experimentally.

Engineering controls for clean air in the office environment.

Supply of adequate amounts of fresh air, properly conditioned, is crucial to maintaining good air quality in the office environment. Building managers frequently attempt to limit the amount of fresh air supplied to offices, because of the energy costs involved. It is important that the amount of fresh air being supplied be evaluated by competent personnel and that substandard conditions be rectified. It is also important that ventilation systems be properly maintained. If these fairly simple steps are taken, many complaints of poor air quality will be eliminated.

Collection of silica and asbestos aerosols by respirators at steady and cyclic flow.

Air purifying dust/mist respirators are presently tested using a silica aerosol under conditions of steady flow. In experiments, the predictive validity of such tests was evaluated by testing respirators using silica and asbestos aerosols under conditions of both steady and cyclic flow. Silica penetration at steady flow was reasonably predictive of silica penetration under cyclic flow. However, asbestos penetration under cyclic flow was not predicted well by penetration of either silica or asbestos at steady flow. Furthermore, the potential for exhalation valve failure under cyclic flow was identified. Current NIOSH protocols for evaluating respirator performance should be reconsidered in light of these findings.

Investigation of reports of sexual dysfunction among male chemical workers manufacturing stilbene derivatives.

A Health Hazard Evaluation was conducted by the National Institute for Occupational Safety and Health in an area of a large chemical plant that manufactured the stilbene derivative 4,4'-diaminostilbene-2,2'-disulfonic acid, an intermediate used for the production of optical brightening agents. Men employed in the area reported problems with impotence. The study population consisted of 44 men aged 20-57 years (mean age 37) employed in the area at the time of the evaluation. An industrial hygiene investigation, health and work history questionnaire survey, physical examinations, and blood chemistry and serum hormone evaluation were conducted. Fourteen percent of the men reported symptoms of impotence over the preceding 6 or more months, 7% had potency problems of shorter duration, and 7% were not currently impotent but had experienced impotence for 6 or more months in the past; 36% experienced decreased libido, all since beginning work in the production area. Low levels of serum testosterone (less than 350 ng/dl) were observed in 37% of the men. The low serum testosterone concentrations were not accounted for fully by diurnal variation or an effect of rotating shift work. It is suggested that exposures to chemicals possessing estrogenic activity may be related to the observed health effects in these workers.

Collection efficiency of respirator filters challenged with monodisperse latex aerosols.

Collection efficiency was evaluated for 10 respirator manufacturers' electrostatically-charged dust/mist filters challenged with eight sizes of latex spheres in a range representative of the silica aerosol used in National Institute for Occupational Safety and Health (NIOSH) certification tests. Minimum efficiency occurred at or below the smallest size of 0.102 microns. Appreciable differences were found in the performances of filters distributed by the 10 manufacturers. Filters produced by 1 manufacturer exhibited significantly lower collection efficiency than other filters tested; those produced by 2 manufacturers performed somewhat better than the others tested. Statistical evaluation of Weibull-transformed data using analyses of covariance and Tukey's significant difference test allowed classification of the 10 manufacturers into three performance categories.

Prediction and measurement of velocity into flanged slot hoods.

A model describing the three-dimensional velocity field into a flanged slot hood has been developed using potential flow theory. Modeling the slot as an elliptical aperture allows use of the potential function to develop expressions for the velocity components (vx,vy,vz) at any point (x,y,z). Experiments were performed to measure velocities in front of six slot hoods. Experimental results were compared with velocities predicted by two models: an equal area ellipse with the same length to width ratio as the slot and an ellipse inscribed within the slot.

Development of a sampling and analytical method for measuring the epoxy content of aerosols: II. Application of the method to epoxy-containing aerosols.

Aerosols generated by epoxy spray painting consist of droplets containing partially-cured mixtures of epoxy resins and curing agents, as well as pigments, solvents and diluents. A sampling and analytical method has been developed to measure the epoxy content of these aerosols. The method collects the aerosol in a midget impinger containing dimethyl formamide, which inhibits the curing reaction between the epoxy and curing agent, preserving the unreacted epoxy functional groups present in the aerosol. The impinger contents are analyzed by reacting the epoxy with an excess of bromide generated in situ from tetraethylammonium bromide, and measuring the unreacted bromide in the reaction mixture by normal pulse polarography. The precision and accuracy of the method have been evaluated using a pure epoxy resin as a model compound. The method was applied to aerosols containing mixtures of epoxy resin and amine curing agents in various degrees of cure, to aerosols containing large quantities of nonepoxy compounds, and to aerosols of epoxy surface coatings. The method is capable of precise and accurate measurement of epoxide functionality, and it applicable to the measurement of epoxy-containing aerosols in spray finishing operations.

Empirical validation of theoretical velocity fields into flanged circular hoods.

Previously presented theoretical models of the three-dimensional velocity field into a flanged circular hood, both with and without crossdraft, are examined by hot film anemometry. A final model with empirical modifications is selected and validated. Computer generated streamline maps, which enable visualization of the effects of crossdrafts on hood performance, are presented. The theoretical basis for capture efficiency using the model is discussed.

Determination of occupational exposure to fabric brightener chemicals by HPLC.

Paired-ion reversed-phase liquid chromatography was applied to the problem of determining the exposure of chemical workers to aerosols of chemical intermediates in the production of fabric brighteners, specifically: 4,4'-diaminostilbene-2,2'-disulfonic acid, disodium salt (DAS), 4,4'-dinitrostilbene-2,2'-disulfonic acid, disodium salt (DNS), and paranitrotoluene sulfonic acid, sodium salt (PNTSA), which are all light-sensitive ionic compounds. Personal samples were collected on Teflon-coated glass fiber filters through which air was drawn at 1.7 Lpm. DAS, DNS and PNTSA were desorbed quantitatively in water from the filters. Tetrabutylammonium phosphate served as the ion-pairing reagent to these anions and was added to the eluent solutions. The samples were separated on an octadecylsilyl column with a methanol/water gradient. These three compounds eluted with good separation in 15 min. Monitoring absorbance of light at 254 nm, one can easily obtain detection limits of 2 micrograms/mL or less. Air concentrations of 0.02 mg/m3 were measured readily by personal sampling. Airborne exposures in this facility were found to range from nondetectable levels up to 60 micrograms/m3 DAS. A fixed high volume sampler collected between 0.2 and 2 micrograms/m3 each of DAS, DNS and PNTSA. The enclosure of the reactors and transport of materials in solution or as a slurry minimize exposure.

Capture efficiency of local exhaust ventilation systems.

A new technique to measure the performance of local exhaust ventilation systems has been developed and tested in both the laboratory and the field. The technique involves the measurement of the capture efficiency of exterior hoods, defined to be the fraction of contaminants given off by a process captured by the exhaust system serving that process. Capture efficiency measurement can be a powerful tool in the evaluation of local exhaust systems, since it is a direct, quantitative measure of system performance; in contrast, indices of performance now in use are either qualitative or measure quantities which may not be related directly to system performance. A basic theory for capture efficiency has been developed, and a prototype system for measuring capture efficiency has been constructed and tested. Preliminary laboratory and field measurements using the system have demonstrated the power of the method, which should find widespread use in the design of new ventilation systems and the evaluation of existing ones.

A critique of the U.S. standard for industrial exposure to sodium hydroxide aerosols.

Published studies of the toxicity of sodium hydroxide aerosols are few. These studies were generally marred by inadequate characterization of particle size and chemical compositon and of the ambient humidity. Because NaOH aerosols can readily undergo reaction with carbon dioxide to form sodium carbonate, a much less alkaline (and less hygroscopic) compound, these shortcomings may warrant a reconsideration of the NaOH standard and the consideration of a Na2CO3 standard.