The World Health Organization (WHO) has warned that air pollution is significantly more damaging than previously thought, as it reduces the maximum permitted levels of dangerous chemicals. Before the COP26 summit in November, it is asking its 194 member states to reduce emissions and take action on climate change.

Toxic particles and gases can affect humans in considerably lower amounts than previously thought, which is poor news for anyone who has heart or lung problems. As a result of the adjustments, the UK’s regulation limits for the most dangerous pollutants are now four times higher than the WHO’s maximum levels. The problem is that the most dangerous pollution, microscopic particles that can go into the lungs, is extremely difficult to remove.

Heart disease and stroke have been linked to air pollution. It can harm a child’s lung development and make asthma worse. “Improving air quality can help with climate change mitigation efforts,” according to the WHO, “while decreasing emissions will help with air quality.”