PAH free standard 是什么意思

PAHs are a group of chemicals that are formed the incomplete burning of coal, oil and gas, garbage, or other organic substances.
多环芳烃是一组化学物质，他们是由未经完全燃烧的煤. 油和气. 垃圾. 或是其他有机物质形成的。

PAHs can be formed through natural processes or those related to human activies
多环芳烃可由自然过程或与人类活动相关的确行为造成。

There are more than 100 different PAHs.Most PAHs do occur alone in the environment. Rather they are found as mixtures of two or more PAHs
有超过100种.10，000个不同的多环芳烃化合物。绝大多数的多环芳烃在环境中不是单独存在，它们往往是两个或更多的多环芳烃的混合物。

Thete can also be found substances such as crude oil,coal,creosote,and road/rooging tar
它们还可以在一些物质中，如原油，煤，杂芬油，和焦油（沥青）等

Toxicity
毒性

Although unmetabolized PAHs can have toxic effects,the major concern in animals is the ability of reactive metabolites to bind to proteins and DNA.
虽然非代谢变化的多环芳烃有毒性反应，但主要涉及在动物的蛋白质和DNA的代谢反应的能力。

Four,five and six ring PAHs have greater carcinogenic potential than do two,three or seven