car exhaust

Atmospheric levels of a little known by-product from diesel engines are up 70 times higher than expected according to a study.

Researchers found that long-chain hydrocarbons are significantly under-reported in car manufacturers' data.

These hydrocarbons are a key component of two of the worst air pollutants, ozone and particulate matter.

The authors believe these "hidden" emissions are having a large impact on air quality in cities like London.