of 10 trials. The overall result was that the station emissions could not be detected against the fluctuating background of S02 from other sources, in spite of the low pollution levels in the Pembroke survey area. A similar analysis of smoke concentration differences between pairs of aligned sites has also been carried out. This failed to reveal any significant increase in smoke concentration at any of the downwind sites during the post-commissioning period 1971-72. From these results we see that the operation of Pembroke Power Station has little effect on air quality as indicated by the smoke and sulphur dioxide concentrations at ground level. ACKNOWLEDGEMENTS Thanks are due to members of Pembroke Power Station staff who carried out the surveys and chemical analyses, and to Warren Spring Laboratory, Stevenage, for converting the raw data into pollutant concentrations. This paper is published by permission of Mr. D.A. Pask, Director General of the South Western Region, CEGB. REFERENCES CLARKE, A.J., SPURR, G., & CATCHPOLE, S. (1966) Towards a Clean Air Policy. Proc. of International Clean Air Congress, London, October 1966. JARMAN, R.T., & DE TURVILLE, C.M. (1976) Routine Sulphur Dioxide Surveys around Large Modem Power Station. Part II: Fawley and Pembroke. Atmospheric Environment, 10, 269-275. CEGB, Bedminster Down, Bridgwater Road, Bristol BS13 8AN Red Kite Leighton Moses