Atmospheric halocarbons: A discussion with emphasis on chloroform

Bleaching of paper pulp represents a major industrial use of chlorine and could provide an environmentally significant source of atmospheric halocarbons. The related global production of chloroform is estimated at 3 × 10 5 ton yr −1 and there could be additional production associated with atmospheric decomposition of perchloroethylene. Estimates are given for the production of methyl chloride, methyl bromide and methyl iodide, 5.2 × 10 6 , 7.7 × 10 4 , and 7.4 × 10 5 ton yr −1 respectively. The relative yields of CH 3 Cl, CH 3 Br and CH 3 I are consistent with the hypothesis of a marine biological source for these compounds. Concentrations of other halocarbons observed in the atmosphere appear to indicate industrial sources.