Toluene estimating exposures

Important commercial isocyanates include the diisocyanate monomers toluene diisocyanate (TDI), methylene diphenyl diisocyanate (MDI), hexamethylene diisocyanate (HDI), and MDI-, TDI-, and HDI-based isocyanates (e.g., prepolymers and polyisocyanates). World-wide production volume is estimated at over 12 billion lb. Isocyanates (diisocyanates, polyisocyanates, and prepolymers) all cause similar health effects, most commonly asthma [32]. Isocyanates are reported to be the leading attributable cause of work-related asthma [16]. Isocyanates are potent sensitizers that can trigger a severe and potentially fatal asthma attack in sensitized persons at very low isocyanate exposure levels [16]. Toluene diisocyanate is reasonably anticipated to be a human carcinogen by National Toxicology Program. 

Several authors have pointed out that the urinary excretion of hippurate is a poor indicator of exposure to toluene at 200 ppm [760 mg/m ] or lower (Jonai Sato, 1988 Too et al., 1991 Pierce et al., 1996). Therefore, data on ethnic differences in hippurate or cresol excretion in urine at these low exposure levels (e.g., Inoue et al., 1988) are of doubtful significance. Toluene level in expired air may be a more reliable parameter (Foo et al., 1991). Although at the level of the individual, data on urinary hippurate cannot be reliably used to estimate low toluene exposures, they can be used at the group level to establish whether at a certain location the toluene exposure remained below a particular threshold (Lauwerys, 1983). 

In the Montreal case-control study carried out by Siemiatycki (1991) (see monograph on dichloromethane in this volume), the investigators estimated the associations between 293 workplace substances and several types of cancer. Isocyanates were one of the substances, and it was stated that the most common form in this study was toluene diisocyanates. The main occupations to which isocyanate exposure was attributed in this study were motor vehicle refinishers, motor vehicle mechanics and foundry workers. Only 0.8% of the study subjects had ever been exposed to isocyanates. For most types of cancer examined (oesophagus, stomach, colon, rectum, pancreas, prostate, bladder, kidney, skin melanoma, lymphoma), there was no indication of an excess risk due to isocyanates. For lung cancer, in the population subgroup of French Canadians (the majority ethnic group in this region), based on 10 cases exposed at any level, the odds ratio was 2.2 (90% CI, 0.9-5.3). [The interpretation of the null results has to take into account the small numbers and presumably low exposure levels. Workers had multiple exposures.]... 

As noted before, the most significant refinery emissions were airborne. For those options that involved a change in emissions affecting air quality, impacts were modeled using standard air dispersion techniques. Exposure estimates were developed for three classes of chemicals (1) benzene, toluene, ethylbenzene and xylene (BTEX), (2) other chemicals reported in the refinery s TRI submissions, and (3) criteria pollutants (SO2, NO2, PMjo, and CO). Similar modeling techniques were used for all three classes. The project focused on the impact of benzene emissions, since benzene turned out to be the chemical species of greatest concern relative to other releases. 

Toluene and xylene have inhalation reference concentrations (RfCs) of 0.4 and 0.1 mgm, respectively. The RfC is an estimate of a daily inhalation exposure of the human population that is likely to be without an appreciable risk of harmful effects over a... 

KeU (USA) 1998 Parts washing operation Toluene Exposure estimate range (mg/m )... 

Kudla (USA) 1997 Analysis of historical exposures to two workers with bone marrow disorders in the printing trade Benzene, toluene Detailed worker interviews and workplace descriptions Qualitative estimates generated... 

Hawkins, N. C., and Evans, J. S. (1989). Subjective estimation of toluene exposures A calibration study of industrial hygienists. Appl Ind Hyg 4, 61-68. 

An estimation of the internal pressure of RT untreated containers after eight hours of toluene exposure can be made based on the toluene volumes lost due to permeation and sorption. The result is a vacuum of 7.7 trnn Hg, where the 1.4 g. of solvent sorbed into the HDPE walls is the dominant factor. This indicates that during the early period of solvent exposure simple sorption of the solvent into the polymer can generate conditions leading to paneling in untreated HDPE containers. 

PU are compounds formed by reacting the polyol component with an isocyanate compound, typically toluene diisocyanate (TDI) methylene diisocyanate (MDI) or hexamethylene diisocyanate. Polyols are relatively non-toxic (i.e., polyether type polyols are found to be safe, because they are low in oral toxicity with almost no irritation effect to the eyes and skin), however, isocyanates are highly toxic and the product can have a significant toxicity if remnants of isocyanate are in it, which manifests itself mainly as a respiratory (as well as a dermal) hazard. Exposure to the vapour of isocyanates directly may cause irritation for the eyes, respiratory tract and skin. Such an irritation may be too severe to produce bronchitis and pulmonary oedema. As health hazards of isocyanates are considered, one immediately remembers one of the worst industrial disasters of the 20th century, that occurred in Bhopal, India, because of the toxic cloud of methyl isocyanate was released accidentally from the Union Carbide pesticide factory in December 1984. An estimated 3,000 people died immediately with a final of some 20,000, most suffocating from the cloud s toxic chemicals, and some 50,000 were injured, most were residents living near the plant. 

Most of the selected female reproductive toxicology studies examined explicitly stated chemical exposure levels either as parts per million, stratifying as to number of days of exposure, or as estimates of the percentage of the threshold limit values. Medline, Toxline, and Dissertation Abstracts databases were utilized to search for all research papers published in any language from 1966 to 1996. In total, 559 studies were obtained from the literature search. Of these, only 21 studies explicitly stated some sort of exposure level for the various chemicals. These chemical exposure levels in the literature and subsequent pregnancy outcomes were compared to lOL chemical exposure indices. The following is an example of one of the many chemical exposures encountered, namely exposure to toluene. For other compounds, Table 20.3.5 contrasts values in the literature with lOL indices of chemical exposure. 

Holmberg et al. and Tikkanen eonsidered workers substantially exposed if flieir estimated continuous exposure had been at least one-third of the current TLV concentration or if the estimated peak exposure had reached the TLV concentration. Similarly, Ng described high concentrations of toluene (mean 88, range 50-150 ppm) exceeding current standards. All these exposure levels for toluene exceed the current frueshold limit value. lOL toluene exposure levels are considerably lower than any value reported in the literature. 

Gas samples from room air were also detected with PTR-MS to estimate the indoor air quality [4,123]. Samples were taken from five rooms constructed more than 20 years ago. Two rooms had been equipped with new furniture and carpets only 2 months before the measurements were done. The concentrations of formaldehyde and ethanol were quite similar in the old and newly furnished rooms. Acetaldehyde, methanol, propanol, acetone, and toluene were strongly enhanced in the two newly furnished rooms. It was also found that the concentration of formaldehyde in four of the five rooms was higher than the maximum concentration allowed by Austrian law for permanent exposure dose to human [4]. 

Estimated values see text, b From Ribo and Kaiser (1983). c From Curtis et al. (1982), 5-min exposure value, d From Kaiser and Ribo (1985). e Recrystallized from hexane, f Recrystallized from toluene, g From Kaiser et al. (1985). h This work. 

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