Unintentional increases in air pollution may arise from efforts to reach net zero emissions in the UK Marcin Rogozinski/Alamy

A widespread switch to burning hydrogen to heat UK homes has been suggested to meet the country’s new climate targets – but a leaked report has warned the government that such a move risks inadvertently releasing harmful nitrogen oxide (NOx) pollution in densely populated towns and cities.

An unpublished report by air quality experts for the Department for Environment, Food and Rural Affairs (Defra) lays out the pros and cons for air pollution stemming from the UK’s new legal target of cutting …