Q1

　　What is the major dietary source of PAHs ?

　　PAHs的主要膳食来源是什么?

　　A

　　Major dietary contributors of PAHs depend on the consumption pattern (amount and types of food consumed) and the levels of PAHs in foods. According to the Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives (JECFA), cereals and cereal products, vegetables fats and oils are major contributors to dietary exposure to PAHs.

　　PAHs的主要膳食来源取决于食物消费模式（食物消费量及食物种类）及食物中PAHs的含量。联合国粮食及农业组织／世界卫生组织联合食物添加剂专家委员会（专家委员会）指出，谷物及谷类食物、植物脂肪和油类是摄入PAHs的主要膳食来源。

　　Q2

　　Why is food contaminated with PAHs?

　　为什么食物会受PAHs的污染?

　　A

　　PAHs may be formed during incomplete combustion or burning of organic matters. Almost all food contains PAHs to a certain extent.

　　The two major sources of B[a]P (a type of PAH) in food are deposition and uptake of B[a]P from polluted air on food crops and formation and deposition of B[a]P during heat processing using methods such as roasting, smoking, and grilling.

　　Levels of B[a]P may vary depending on the processing conditions and are often higher in barbecued/smoked meat or fish. Furthermore for fats and oils, drying of cereals and plants used for production of crude vegetable oils using direct application of combustion gases can result in contamination of the products with B[a]P as combustion products may come into contact with the grain, oil seeds and thus increasing B[a]P level in the oil product. The level of B[a]P in oil would be much reduced after oil refining processes and the ultimate level of BaP would depend on the conditions under which refining takes place and quality control.

　　在不完全燃烧有机物质的情况下会产生PAHs。几乎所有食物都含有一定程度的PAHs。

　　食物中苯并[a]芘的两个主要来源是农作物吸收了受污染空气中沉降的苯并[a]芘及食物在烘焗、烟熏和烧烤等加热过程中产生和积聚的苯并[a]芘。

　　食物的加工条件对产生多少苯并[a]芘也有影响。烧烤／烟熏肉类或鱼类的苯并[a]芘含量通常较高。此外，在烘干供制作植物毛油(未经精炼的油)的谷物和植物时，如果直接使用燃烧产生的气体烘干谷物和植物，谷粒和油籽会接触到燃烧所产生的物质，从而引致食油产品受苯并[a]芘汚染。不过，在食油的精炼过程中，能把苯并[a]芘含量大大降低，而苯并[a]芘最终的含量则取决于精炼的条件及质量控制。

　　Q3

　　Will the B[a]P level in oil increase after repeated deep-frying ?

　　不停翻炸食油，苯并[a]芘的含量会否上升?

　　A

　　There are reports which suggest that the level of B[a]P in oil will increase after repeated use. Since many factors can lead to high levels of B[a]P in oil, one cannot judge if oil had undergone repeated use just by the level of B[a]P in it.

　　有文献指出，翻用食油会增加苯并[a]芘的含量。但由于多种因素可引致食油中苯并[a]芘含量高，所以不能根据食油中苯并[a]芘的含量来判断食油是否为翻用食油。

　　Q4

　　Does the existence of B[a]P in oil mean that the oil had undergone high heat treatment, which in turn means that the oil had been used for frying food previously? Does that equal to “gutter oil”?

　　食用油含苯并[a]芘，是否意味油曾经过高温处理，即可能曾经炸过食物?又是否等同地沟油或坑渠油?

　　A

　　No. The presence of B[a]P in oil can be due to many different factors. Plant materials for oil production can be contaminated through deposits from air. The level of B[a]P in these materials can also increase through drying process using direct application of combustion gases. Furthermore, B[a]P level in oil may increase upon repeated use.

　　不是。因为食用油中的苯并[a]芘，可能经多种不同因素产生。油料作物可以受到空气中的苯并[a]芘沉降污染。而在这些作物的烘干过程中直接使用燃烧产生的气体，亦会最终使食油的苯并[a]芘含量升高。此外，翻用食油也有机会增加苯并[a]芘的含量。

　　Q5

　　What amount of B[a]P consumed will be harmful to health ?

　　食用多少苯并[a]芘会对健康有害?

　　A

　　B[a]P is toxic to genes and can cause cancer in human. B[a]P is classified as “carcinogenic to human” (i.e. Group 1 agent) by the International Agency for Research on Cancer (IARC) of the World Health Organization in 2009. Therefore, a safety reference value cannot be determined for B[a]P. To reduce the health risk associated with B[a]P, efforts should be made to minimise exposure to B[a]P as far as practicable.

　　苯并[a]芘对人类基因有害，并会致癌。苯并[a]芘被世界卫生组织的国际癌症研究机构于2009年列为「令人类患癌」（即第一组）的物质。因此，不能厘定苯并[a]芘的安全参考值。为了减少因苯并[a]芘引致的健康风险，应尽量减少摄入苯并[a]芘。

　　Q6

　　Is there any advice on reducing exposure to B[a]P ?

　　市民可如何减低苯并[a]芘的摄入量?

　　A

　　Public should maintain a balanced and varied diet, which includes a wide variety of fruits and vegetables; Do not use reused cooking oil; avoid overindulgence in barbecued meat, particularly charcoal grilled meat and smoked meat/fish; and remove charred parts of food. Public may reduce consumption of fats and oils to reduce B[a]P exposure.

　　市民应保持均衡及多元化饮食，进食多种蔬果；切勿翻用食油；切勿过量进食烧烤肉类，尤其是炭炉烤制的肉类及烟熏肉类／鱼类；以及切除烧焦部分。市民亦可减少食用脂肪和油，以减少摄入苯并[a]芘。

　　（来源：香港食物安全中心）

　　统筹：宁可儿

　　美编：晓马哥

　　往期精选【戳下方标题】

　　《不想被“疟”？你得防着这对“凶手”！》

　　《了解您最想知道的预防接种知识，还有机会拿大奖~》