asked the Secretary of State for the Environment what assessment he has made of the effects of increasing levels of ammonia pollution in the United Kingdom on concentrations of sulphate aerosols in the air.

In principle, increasing levels of ammonia might be expected to increase concentrations of sulphate aerosols in the air. However, the chemistry of the link is very complex, and there have as yet been no credible quantitative assessments. This is the subject of active research, including work at Harwell laboratory for the Department.