Effects of SO2 and its derivatives on health and ecology: Reports of two working groups. Volume I—human health. Volume II—natural ecosystems, agriculture, forestry and fisheries, November, 1981. (Study sponsored by the International Electric Research Exchange. Copies of executive and technical summaries available from IERE, c/o P.O. Box 50490, Palo Alto, CA 94303, U.S.A. Full reports available from national addresses listed in summaries.)