Uttaradit is the northern province with the greatest risk of lung cancer due to its bad air pollution.
PAHs, or polycyclic aromatic hydrocarbons, including the carcinogen benzo(a)pyrene, were being emitted in the air through incomplete combustion by auto engines rather than smoke from forest fires or outdoor burning, Assoc Prof Siwat Pongpiajun, NIDA's head of the Centre for Research and Development of Disaster Prevention and Management said yesterday.
Citing test results of air samples from nine upper northern provinces collected from November-December 2012, Siwat said Uttaradit had the worst PAH problem with 445 picograms per cubic metre of air, followed by Lampang with 87, Phrae with 46, Chiang Mai with 25, Chiang Rai with 21, Phayao with 1.55, Nan with 0.8, Lamphun with 0.45 and Mae Hong Son with 0.1.
Another batch of air samples collected during last March’s haze crisis found that Uttaradit air had 344 picograms of PAHs, followed by Phrae at 91 and Lamphun at 46. The safe limit is 250 picograms.
The average amount of benzo(a)pyrene in the nine northern provinces was 563 picograms – higher than countries including Singapore, Belgium and the United States, but still lower than Hong Kong and China’s Shantou and Guangzhou.
The fact that PAHs went down during the haze crisis suggests that smog might not be the main generator of the 2.5-micron dust particles that carry PAHs. The fine dust was created by high temperature and high pressure like during gas combustion.
However, brushfires and haze could not be totally ruled out as a cause of cancer, pending further study.
“In the big cities, if the governing body wants to take care of people’s health, it should improve the public transport system, not promote people to use cars. Because many cars cause congested roads and also create air pollution,” he added.