Study of workplace

Another potential source of asbestos release to air is from clutches and brakes on cars and trucks a wide range of air concentrations of asbestos fibers (0.004-16.0 f/mE) has been reported in numerous air sampling studies of workplaces during maintenance and replacement of vehicle brakes (WHO 1998). Release of asbestos from insulation or other building materials is discussed in Section 6.4.1, below. Estimated asbestos emissions from waste disposal from all sources were about 499,000 pounds... 

Human experience. Human experience is often regarded as the most useful and the most relevant source of information, but does vary considerably in both quality and quantity. For some solvents which have been in use in large quantities for many years, extensive studies of workplace health (known as epidemiology ) may have been carried out. These studies may either have identified adverse effects or have shown the absence of such effects. A shortcoming is often the extent and quality of exposure estimation, absence of which considerably reduces the value of the study. Useful human data may also be available from studies in volunteers exposed to low levels. Individual case reports of adverse effects are of limited value, but may well indicate the need for further more detailed study. 

For example, within organisation science, the study of practice has emerged, illuminating a degree of tension between studies of workplace activity without evaluation of practice, and normative accountability, what counts or could be evaluated as competent or exemplary practice (Gherardi, 2009). However, the study of practice has, as one its main aims, a theoretical framework within which to understand practice in a general sense, rather than to inform practitioners in one specific discipline. 

Experimental methods coming from laboratory-based studies of worst-case testing of simulated workplace conditions. 

In contrast, three European studies have found slight but statistically significant increases in cancer in workers exposed to trichloroethylene. A survey of Finnish workers exposed to primarily trichloroethylene found an association of limited statistical significance between exposure and incidence of stomach, liver, prostate, and lymphohematopoietic cancers (Antilla et al. 1995). However, the study did not reliably separate the effects of individual solvents, so attributing these cancers to trichloroethylene exposure alone was not possible. A significant association between workplace exposure to trichloroethylene and kidney cancer was found in a retrospective cohort study of German cardboard factory workers (Henschler et al. 1995). The... 

Acute-Duration Exposure. Information is available regarding the effects of acute-duration inhalation exposure of humans to acrylonitrile and the effects are characteristic of cyanide-type toxicity. Quantitative data are limited but are sufficient to derive an acute inhalation MRL. Further studies of humans exposed to low levels of acrylonitrile in the workplace would increase the confidence of the acute MRL. Studies in animals support and confirm these findings. No studies are available on the effects of acute-duration oral exposure in humans however, exposure to acrylonitrile reveals neurological disturbances characteristic of cyanide-type toxicity and lethal effects in rats and mice. Rats also develop birth defects. Animal data are sufficient to derive an acute oral MRL. Additional studies employing other species and various dose levels would be useful in confirming target tissues and determining thresholds for these effects. In humans, acrylonitrile causes irritation of the skin and eyes. No data are available on acute dermal exposures in animals. 

The quality of life experienced by people with MCS is shaped, to a great extent, by the level of awareness of environmental health issues where they live and work. Some are recipients of workplace accommodations in accordance with the Americans with Disabilities Act others are harassed and ostracized at work, or fired from their jobs. Some disabled by chemical exposures in the workplace receive workers compensation the majority of chemical-illness claims are denied. Some cities, schools and other institutions have adopted fragrance-free policies and Integrated Pest Management (IPM) programs to reduce chemical barriers and dangers in public places others still resist despite all the prevalence studies and research indicating that MCS is a serious threat to public health. 

When epidemiological studies form the basis for the risk assessment of a single chemical or even complex mixtures, such as various combustion emissions, it may be stated that in those cases the effects of combined action of chemicals have been incorporated. Examples can, for instance, be found in the updated WHO Air Quality guidelines (WHO 2000). Thus, the guideline value for, e.g., ozone was derived from epidemiological studies of persons exposed to ozone as part of the total mixture of chemicals in polluted ambient air. In addition, the risk estimate for exposure to polycyclic aromatic hydrocarbons was derived from studies on coke-oven workers heavily exposed to benzo[fl]pyrene as a component of a mixture of PAH and possibly many other chemicals at the workplace. Therefore, in some instances the derivation of a tolerable intake for a single compound can be based on studies where the compound was part of a complex chemical mixture. 

A study of 9076 US miners ftom 1969 to 1971 showed an overall prevalence of CWP of 30%, with PMF occurring in 2.5% of the sample. A more recent study of US coal workers through 1988 has found a reduction in the incidence of pneumoconiosis coinciding with a reduction in workplace exposures to 2 mg/m after 1969. In Britain, the prevalence of all categories of CWP in working miners has fallen ftom 13.4% in 1959-1960 to 5.2% in 1978 for PMF, the rate in 1978 was 0.4%. ... 

Humans may be exposed to 2-hexanone through contaminated air in the workplace and in the vicinity of hazardous waste sites and consumption of and dermal contact with contaminated water, especially in the vicinity of hazardous waste sites. Epidemiological studies that followed populations exposed to 2-hexanone, either in the vicinity of hazardous waste sites or in the workplace, would be useful in assessing adverse health effects in humans. In any such studies, emphasis should be placed on neurological, hematological, immunological, reproductive, and developmental effects. Similarly, human dosimetry studies of these populations would be useful in associating 2-hexanone levels with the reported effects. 

Chlorine dioxide degrades rapidly in air (see Seetion 6.3.2.1) and should be measurable only near its source of production or use (e.g., pulp and paper mill plants, water treatment facilities). As part of an international study of workers in the pulp and paper industry, the concentration of chlorine dioxide was measured in the workplace air of pulp and paper mills from 19 countries. The concentration of chlorine dioxide was measured in the following work areas steam and power generation (range, <0.001-0.06 ppm) effluent water treatment (range, not detected to 0.003 ppm) and maintenance (range, <detection limit to 5.8 ppb) (Kauppinen et al. 1997 Teschke et al. 1999). In another study, the concentration of chlorine dioxide was measured in the workplace air at a pulp mill in British Columbia, Canada between May and June, 1988. The concentration of chlorine dioxide was <0.01 ppm in area samples and personal full-shift samples. The exception was in the bleach/chemical preparation area sample in which the concentration of chlorine dioxide ranged from <0.01 to 0.3 ppm (Kennedy et al. 1991). 

The presence of chemicals as intermediates, additives or contaminants in the workplace implies co-exposure to complex, often varying mixtures of potential carcinogens other than the compound of interest. Thus, when epidemiological studies of populations with mixed and complex exposures find positive results, it is often difficult to ascribe causality to a single agent, and for many compounds it may never... 

Studies of working women present the potential for additional bias, because some factors that influence employment status may also affect reproductive end-points. For example, because of child care responsibilities, women may terminate employment, as might women with a history of reproductive problems who wish to have children and are concerned about workplace exposures (Joffe, 1983 Lemasters Pinney, 1989). Thus, retrospective studies of female exposure that do not include terminated female workers may be of limited use in risk assessment, because the level of risk for some of the outcomes is likely to be overestimated (Lemasters Pinney, 1989). 

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