Helen ApSimon is Professor of Air Pollution Studies at Imperial College London. Her research in air pollution developed from modelling studies of nuclear accidents, and diversified into international issues such as acid rain, and air pollution problems in Eastern Europe. She has worked extensively for Task Forces under the UN ECE Convention on Long-Range Transboundary Air Pollution, undertaking modelling and and assessment of cost-effective strategies to reduce acidification, eutrophication, excess tropospheric ozone, and fine particulate concentrations. This has led to the Integrated Assessment Unit in the Centre for Environmental Policy, investigating future scenarios for emissions of atmospheric pollutants, atmospheric dispersion and mapping of atmospheric concentrations and deposition, impacts on human health and ecosystems; and costs and benefits of potential air pollution mitigation strategies taking account of simultaneous implications for climate policies. She also has strong interests in urban air pollution, particularly in London, where she co-founded the APRIL (Air Pollution Research In London) network and chairs the subgroup on emissions, modelling and measurements. She has been a member of numerous expert groups and committees, including the Airborne Particles Expert Group, the National Expert Group on Transboundary Air Pollution, and the Air Quality Expert Group of DEFRA. She has recently joined the expert panel of the Airports Commission. Her work is highly interdisciplinary, linking science and policy development.