The UK has made much progress in its efforts to clean the air of toxic pollutants, but while the thick, dirty haze of the 1952 great London smog no longer fills the city streets, air pollution remains a silent killer. In the UK, poor air quality is responsible for some 40,000 deaths each year. It has been linked to diseases such as cancer, asthma, stroke and heart disease, diabetes, obesity and dementia. The health problems from exposure to air pollution are costing the nation more than £20 billion every year.