Document 3Q3ZNxG4V9X2Oq4GNRog3vn5x

(Reprinted from Nature, Vol. 208, No. 5017, PP. 1317 1318, December 25, 1965) Organochlorine Pesticides in the Atmospheric Environment Pollution of tho environment has long boon a subject of public concern and much attontion has been paid recently to the now ecological factors introduced by the wide agricultural usage of posticidal chemicals. Contamin ation of soil and crops has ofton featurod in environmental studies of these pesticides, but so far little attention has been given to atmospheric pollution, although, as long ago as 1961, Harris and Lichtenstein1 showed that tho loss by volatilization of aldrin, dieldrin, heptachlor and gamma- benzene hexachloride was a major factor in their disap pearance from soils treated with these compounds. Later, in the United States, the President's Science Advisory Committee drew attention to tho fact that inhalation of air contaminated with pesticides might present a hazard to man* and rocommended that air should be continuously monitored for pesticide residue levels. In 1965, an Advisory Committee of the United States Food and Drug Administration referred to studies which showed the presence of up to 0-075 p.p.m. of dieldrin in total diets* and considered tho possibility that half as much again could be absorbed from "air or other exposures". Little practical work seems to have been undertaken to determine pesticide residues in the atmospherio environ ment, but in the United Kingdom, Wheatley and Hard man1 recently reported indications of the presence, of organochlorine insecticides in rain-water collected in an agricultural area at Wellesboume in Warwickshire. Steps were therefore taken at this Laboratory to examine rain water collected in the Metropolitan aroa. ' Two collecting stations were set up in Central London, one being on the roof of the Laboratory of the Government Chemist in Lambeth, S.E.l, and approximately 20 m above ground-level. The other was set up, with the co operation of the Meteorolbgical Office, at the London Weather Centre's station on the roof of State House, High Holbom, W.C.l, some 53 m above ground-level and about 1-45 km distant from the other station, across the River Thames. At these two stations, rain was col lected in all-glass apparatus, with amber-coloured receiving vessels to reduce the incidence of photochemical degrada tion*. Samples were removed monthly for examination.' The organochlorine pesticides in the water were determ ined by a gas-liquid chromatographic method using electron-capture detection and silicone and `Aplezon' columns as described by do Faubert Maunder et al.*. The limits of detection by this method were 5 parts per million- million for the isomers of benzene hexachloride (BHC) and 10 parts per million-million for the other organo chlorine pesticides in general use in the United Kingdom. QSft STLCOPCB4060778 Table l. Oroanochlorine Pesticide Residue Levels in Rais-water (Parts per million-million) Station--Cornwall House, London, S.E.l . Month 1005 Feb. Mur. Apr. May June July . aB1IC 10 15 30 20 - 30 25 * BHC 00 -- -- 65 -- -- yBHC 90 GO SO 7C1 55 40 HEOD (dieldrin) 50 GO 50 95 25 10 PP'DDE 70 20 -- -- -- 15 PV' TDE -- -- .-- -- 15 85 Station--Stato House, High Holborn, London, W.C.l Month 1965 Mar. Apr. May June July Rain (mm) 33-4 37-3 36-6 30-2 78'0 aBHC 10 20 20 20 30 BHC -- -- 25 -- "f y- HEOD pp'- BHC (dieldrin) DDE 20 20 _ 70 70 ____ 55 50 155 20 ____ -70 15 10 t5e _ 100 -- 50 20 London pp'. DDT 400 115 300 100 70 85 $>T ____ 140 220 125 80 Tho results for the months of February to July 1965, expressed in parts per million-million, are given in Table 1. Becauso of the small amounts of rain collected and the low levels of tho pesticidos found, it was not possible to confirm the results obtained for tho individual samples by an alternative technique. However, at the end of the 6 months, the combined residues from each station were examined by thin-layer chromatography on silica-gel plates with hexane : acetone, 99 : 1, as mobile phase. The appropriate areas of the chromatoplates were eluted and the soparate eluatos individually re-injected on to the gas-liquid chromatograph in columns. In this way, the presence of dieldrin, pp'-DDT and the a- and y-isomers of BHC was confirmed for both stations. The identity of the pp'-DDT from both stations was further confirmed by conversion to pp'-DDE by treatment with ethanolio potassium hydroxide7. The pp'-DDE formed by this reaction was identified and determined by gas-liquid chromatography. Insufficient quantities of the residues wore available to confirm the presence of (J-BHC, pp'-TDE and pp'-DDK by alternative techniques or to make an infra-red study of any of the residues*. . Some individual rain-water samples vhich had been taken between September 1964 and January 1965 at a number of other places in the British Isles were also examined. The collecting sites ranged from Stornaway in tho Outer Hebrides to Camborne in Cornwall, and tho sampled showed residues of orgariochlorine pesticides in amounts similar to those found in London rain-water. Samples of snow collected in different suburban areas within 25 km of London gave similar results. The size of these other samples, and the low levels found, again precluded the application of any confirmatory tochniquo to the individual samples, but by appropriate bulking of tho residues it was possible to confirm, by thin- layer chromatography, the presence, in the rain-wator DSW 255088 and in the snow, of dieldrin, pja'-DDT and the a- and y-isomers of BHC. The levels at which these pesticides have been detected aro extremely low, near to the limits of sensitivity of the. delicate electron-capture detection system used. Strict precautions were taken throughout to ensure that no fortuitous contamination of samples or extracts occurred within the Laboratory. Two samples taken from remote areas of Scotland during periods of heavy rainfall showed practically no residue content and these results suggest that adventitious contamination of samples in the Laboratory was negligible. Present results suggest that the atmosphere carries, either as vapour or by occlusion on dust particles, small amounts of the organochlorine pesticides in common use in the United Kingdom and that they are `scrubbed out' by rain and snow. ' Work is now proceeding to determine the residue levels in air samples, and preliminary results show the presence of organochlorine pesticides in the range of 10-20 parts per million-million. Most of those residues appear to be associated with particulate matter. These experiments may eventually make it possible to determine the respira tory intake by man and to compare the result with his intake from certain foods of known pesticide-levels*. We thank the Director-General of the Meteorological Office for permission to quote from the London Weather Centre's records of the rainfall on the roof of State House. D. C. Abbott R. B. Harrison J. O'G. Tatton J. Thomson Laboratory of the Government Chemist, Cornwall House, London, S.E.l. ' Harris, C. R,, and Lichtenstein, B. P., J. Econ. Entomol., 54,1038 (1961). * Use of Pesticides, Rep. President's Sci. Advis. Comm. (U.S. Government Printing Office, Washington, 1963). * Rep. Food and Drug Admin. Advis. Comm, appointed to Review Established Tolerances for Residues of Aldrin and Dieldrin on Rato Agricultural Commodities (U.S. Government Printing Office, Washington, 1965). * Wheatley, G. A., and Hardman, J. A., Nature, 207, 486 (1965). * Robum, J., Chem. and Ind., 1555 (1963). ,* de Faubert Maunder, M. J., Egan, Hi, and Robum, J., Analyst, 89 157 (1964). 7 Hamence, J. H., Hall, P. S., and Caverly, D. J., Analyst, 90, 649 (1965). 'Abbott, D. C., Crosby, N. T.. and Thomson, J., Proc. Soc. Anal. Chem. Cong, (in the press). ' * Review of the Persistent Organochlorine Pesticides, Appendix F (H.M.S.Ol, London, 1904). Primed in Great Rritain by Fisher, Knight & Co.. Ltd.. St. Albans. DSW 255089