To the Editor:
We read with great interest the report of Schinset al.1on their controlled human-exposure study of chlorine inhalation. The air pollutant studied, gaseous chlorine, is one of substantial relevance in terms of total industrial usage and involvement in emergency release scenarios.
The authors referred to “…a paucity of human data on the effect of chlorine on the upper respiratory tract”. Their literature review, however, overlooked two recent and pertinent studies from our institution pertaining to the effects of Cl2on both the upper and lower respiratory tracts. D'Alessandroet al.2documented a significantly greater acute bronchial (obstructive) response in asthmaticversusnormal volunteers exposed to 1.0, but not 0.4 parts per million (ppm) Cl2for 15 min2. Shustermanet al.3demonstrated significantly higher nasal irritation ratings and nasal congestion (assessed by rhinomanometry) among seasonal allergic rhinitic volunteers (as compared to normal controls) exposed to chlorine at 0.5 ppm×15 min. A common denominator of these studies is the need to identify potentially susceptible subpopulations in order to provide the most sensitive assay for potential population-based health effects.
The inability of Schinset al.1to document significant subjective complaints in response to Cl2exposures as high as 0.5 ppm×6 h, may relate to the manner in which symptoms were recorded, which did not include baseline (pre-exposure) measures and was tempered by a physician's subjective estimation of the likelihood of relatedness exposure. Moreover, the study did not employ objective physiological measures of nasal irritant response (e.g.rhinomanometry, acoustic rhinometry, nasal peak flow measurement, or rhinostereometry). Given these limitations, the negative findings of the study should be viewed with caution, especially in light of other positive studies with comparable exposure levels that were not discussed.
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