agents. In several of these there has been an attempt to follow-up those who were adversely affected in order to determine the persistence of any immediate abnormalities.

Prominent among these has been the examination of firefighters who have been acutely exposed to a variety of combustion products.²⁰ As might be expected, in a number of the reports only transient pulmonary function changes have occurred.^21,22 In cases where fires involved polyvinyl chloride,²³ isocyanates²⁴ or ''plastics"²⁵ there was evidence of persistent effects ranging from increased symptoms to progressive fatal asthma. A follow-up of survivors of a subway fire suggested persistence of small airway damage and respiratory symptoms at six months and two years.²⁶

In 1985 Brooks, et al., described the clinical condition of reactive airways dysfunction syndrome (RADS).²⁷ The condition is asthma-like but differs from occupational asthma because of an absence of a preceding period for sensitization to occur and the onset of illness after a single overexposure. A single exposure to a glacial acetic acid spill was carefully studied and the relative odds of developing RADS was estimated to be as large as 10 for the highest exposure group. ²⁸ Although no general estimate is available of the probability that RADS will follow from a single high irritant exposure, the number of agents which have been reported is quite varied and includes uranium hexafluoride, hydrazine, heated acids, perchlorethylene and toluene diisocyanate.^27,29,30 The severe disability associated with some of these episodes is disturbing.

In summary, a number of specific agents as well as poorly described irritant exposures have been shown to cause long-term disability and even death after a single severe overexposure. The suggestion is that any severe exposure to a wide variety of respiratory irritants has a reasonable likelihood of producing serious long-term effects on the respiratory system. The exposure circumstances described in this section did not lead to evaluation of asymptomatic exposed individuals. Therefore, the effects of exposures high enough to cause disability in those who were symptomatic do not directly address the question of chronic effects in the absence of acute illness.

In 1956, Schilling published a summary of descriptive studies which elegantly characterized the persisting risk of disease among cotton textile workers.³¹ It was Schilling who also was responsible for the development of the symptom score which still best describes the acute symptom complex—ranging from occasional Monday morning chest