Councils in England are facing legal action for running public health campaigns warning against the use of wood burning stoves. Just under a third of councils in England with the highest concentration of wood stoves have received threats of legal action or lobbying from the Tile Industry Association (SIA), according to freedom of information requests by the BMJ. Other local authorities have received leaflets from the main stove trade group, which claim that burning wood reduces blood pressure and stress. UK government emissions data show that household combustion is the main source of PM2.5 fine particulate air pollution. PM2.5 is particles 2.5 micrometers or less in size. The World Health Organization considers them the most harmful pollutant for human health and a carcinogen.