Interested in this kind of news? Receive them directly in your inbox. Delivered once a week. Sign Up It’s thought that ultrafine particles, which are smaller than the size of a typical virus, could be the most dangerous form of car pollution as they can penetrate deep into the body and have been linked to brain cancer. But currently only solid particles which are larger than 23nm in diameter are regulated - despite regulators knowing for years that cars also emit these tiny particles. The lab tests on the Astra and Qashqai, the second and fourth bestsellers in their segments respectively, showed that when solid particles as small as 10nm were measured the total number of particles rose sharply. On some tests, the emissions of these tiny particles alone were very close to the legal limit for particle number emissions. This means that large amounts of particle pollution are completely neglected by the law, despite potentially being the most harmful to human health. T&E said that the unregulated pollutants - including ultrafine particles smaller than 23 nanometres and pollutants like ammonia which contribute to the formation of regulated particles (PM2.5) - must be included in future testing. The laboratory tests simulated real-world driving and measured a range of pollutants including those which are currently unregulated and difficult to measure on the road, such as ultrafine particles, volatile and semi-volatile particles and ammonia. Anna Krajinska, emissions engineer at T&E, said: ‘Regulated particles are only half the story. The smallest ultrafine particles are thought to pose a bigger threat yet they’re ignored by official tests. The next Euro pollution standard must close the loopholes and set limits for all pollutants. The endgame is a standard that demands zero emissions from cars on our roads.’ The tests also found that regulated particle emissions from the diesel cars spiked to more than 1,000 times normal levels - again exposing the public to dangerous levels of pollutants. The rise in particle numbers occurred when the vehicles cleaned their filters, which can happen in urban areas and last for up to 15km. But a loophole in testing rules means the cars can still pass the official test. With three in four inhabitants of European cities exposed to unsafe levels of particles, particulate pollution is increasingly seen as ‘pollution enemy number one’. It is the type of air pollution most closely associated with cancer, and chronic exposure has been found to affect the heart and the lungs.