Workers at a toluene-diisocyanate manufacturing plant were studied longitudinally to determine the effects of the chemical on their health. Studies included health questionnaire, pulmonary function, environmental monitoring, and immunologic testing. Workers reporting increased lower respiratory symptoms were from the nonsmoker group. Environmental monitoring showed frequent excursions of toluene-diisocyanate concentrations above the threshold limiting value. There was poor correlation between area and personal exposure levels. No exposure-related decline of pulmonary function was demonstrable. Immunologic studies showed development of a positive skin test to a toluene-diisocyanate-human serum albumin conjugate by some persons and an increasing incidence of toluene-diisocyanate-specific IgE antibodies as measured by a radioallergosorbent test. Toluene-diisocyanate did not induce histamine release from leukocytes in vitro but did diminish the in vitro stimulation of cyclic adenosine monophosphate by isoproterenol. Most of the clinically sensitive persons demonstrated adverse bronchial response when challenged by inhalation of toluene-diisocyanate. This response was dose dependent in some persons. When challenged with Mecholyl, clinically sensitive persons showed greater reactivity of airways than nonsensitive persons.

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Four hundred and eighty-six textile workers in three cotton mills and one wool/synthetic mill were studied for symptoms and functional effects of workroom exposure to dust. Byssinosis was found in 5'7% of 386 cotton workers, with an apparent threshold level of 05 mg cotton dust/m3 of air. Mean post-shift functional declines were greater in workers exposed to > 0-2 mg/m3. Workers with byssinosis were unequally distributed, however, with respect to job category and mill; and these variables, rather than current dust exposure levels, accounted for the observed distribution of byssinosis prevalence rates. Variation in biological potency of different samples of cotton dust could be responsible for 'mill effect', the residual variation in response rates by mill after controlling for variation due to dust exposure. A number of other potential influencing variables that are likely to be distributed unequally by mill should also be considered. Mill effect should be assessed in large-scale studies of byssinosis, most of which have analysed biological response rates by combining mill and other variables to examine first-order effects of dust dosage. In such analyses, much of the observed variability may be due to factors other than dust dosage.The relationship between cotton dust exposure and respiratory illness is complicated, but many basic features were recognised more than one hundred years ago. For example, Leach (1863) stated that illness was more prevalent among workers in the early stages of processing cotton, in dustier work places, and in mills using lower grades of cotton. The disabling character of the chronic illness was noted, as was the healthful effect of providing adequate dust control. Despite this fund of sound observations, byssinosis remains an important cause of morbidity and disability. Progress in understanding the disease has been hindered by several problems (US Department of Health, Education and Welfare, 1974). There is no reliable assay for bioactivity of cotton dust. There is lack of agreement on a standard way to measure airborne dust levels. Detection of acute responses to cotton dust has depended heavily on questionnaire data. There is still uncertainty regarding the precise relationship of acute lung function abnormalities or symptom. to the chronic, disabling respiratory disease. There is no clinical marker to distinguish the chronic Received for publication 11 September 1978 Accepted for publication 30 November 1978 disease from chronic airways obstruction ordinarily found in the general population.The present study was undertaken to examine the effects of low current dust exposures, with inclusion of differing past exposures as an independent variable. The method of comparing effects of past exposures was to study mills with different histories of dust control. In examining byssinosis prevalence rates we observed that mill could be a significant influencing variable. Under certain circumstances, failure to control for this variable could lead to faulty analysis of relationsh...

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