研究人員在一項模擬車輛發動或燒烤肉類排放氣體的實驗研究中，發現了致突變性極強的新化合物，是其致癌性母體化合物的數百倍。
科學家從交通工具所排放的廢氣和烤肉中發現新的致突變物質，目前並不清楚這些化合物存在的劑量，也還沒有建立安全暴露標準。美國奧勒岡州立大學等研究機構的研究人員表示，這些化合物過去並不為人所知，不過透過都市的空氣污染和飲食接觸，它們對人體的影響亟需關切。
新發現的「致突變原」（mutagen）是能改變有機體遺傳物質的化學物質，使突變的機率比自然變異高出許多。而突變又常導致癌症，因此這種突變原也算是一種致癌物質。
這項研究的母體化合物是多環芳烴，縮寫是PAHs。PAHs是空氣懸浮粒子上發現的污染物質之一，危險性特別高。其他各種形式的燃燒也都會自然產生PAHs，包括木柴爐灶、汽車發動機、香菸和燃煤電廠。目前已知有許多PAHs是致癌物，例如苯芘。
而當PAHs和氮產生化學反應，就會變成硝化的NPAHs，此時麻煩就更大了。科學家警告，新發現的化合物正是一種NPAHs。研究發現，有一個氮基的NPAHs，其直接致突變性比母體化合物還高6至432倍；有兩個氮基的NPAHs，直接致畸性可比母體化合物還高272至467倍。
這些發現是延伸自科學家Simonich在2008年北京奧運進行的PAHs研究。和部分亞洲城市一樣，北京的空氣污染問題十分嚴重，可能比洛杉磯等部分美國大都市還嚴重10至50倍。基於關切空氣品質對運動員和參觀民眾的影響，當時科學界進行了許多都市空氣品質的研究。
世界衛生組織底下的一個機構去年秋天也宣布，戶外空氣污染具有致癌性，，尤其是懸浮粒子污染，也可能導致其他健康問題。
Newly identified compounds produced by chemical reactions in vehicle exhaust or by grilling meat are hundreds of times more mutagenic than their cancer-causing parent compounds, according to scientists at Oregon State and three other universities.
These compounds were not previously known to exist, and they raise concerns about the health impacts of heavily-polluted urban air and dietary exposure, the researchers said. It is not yet clear in what amounts the compounds might be present, and no health standards now exist for them.
The highly mutagenic compounds were identified in laboratory experiments that mimic the conditions that might be found from the combustion and exhaust in cars and trucks, or the grilling of meat over a flame.
A mutagen is a chemical that changes the genetic material of an organism, increasing the frequency of mutations above the natural background level. As many mutations cause cancer, mutagens are likely to also be carcinogens.
The parent compounds involved in this research are polycyclic aromatic hydrocarbons, or PAHs, formed naturally as the result of almost any type of combustion, from a wood stove to an automobile engine, cigarette or a coal-fired power plant.
Many PAHs, such as benzopyrene, are known to be carcinogenic. PAHs can become even more of a problem when they chemically interact with nitrogen to become “nitrated,” or NPAHs, the scientists warn. The newly-discovered compounds are NPAHs that were unknown until now.
This study found that the direct mutagenicity of the NPAHs with one nitrogen group can increase six to 432 times more than the parent compound.
NPAHs based on two nitrogen groups can be 272 to 467 times more mutagenic than the parent compound.
These discoveries are an outgrowth of research on PAHs that Simonich did at the Beijing Summer Olympic Games in 2008, when extensive studies of urban air quality were conducted, in part, based on concerns about impacts on athletes and visitors to the games.
Beijing, like some other cities in Asia, has significant problems with air quality, and may be 10-50 times more polluted than some major urban areas in the U.S. with air concerns, such as the Los Angeles basin.
An agency of the World Health Organization announced last fall that it now considers outdoor air pollution, especially particulate matter, to be carcinogenic, and cause other health problems as well.
PAHs are one of the types of pollutants found on particulate matter in air pollution that are of special concern.
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