polycycly

例句：

1. 1. Polycyclic aromatic hydrocarbons are a class of compounds that are found in the environment and have been linked to various health effects.
   多环芳香烃是一类存在于环境中的化合物，与各种健康效应有关。
2. 2. Polycyclic aromatic hydrocarbons are also known as PAHs, which refer toa group of chemicals that can be toxic to humans and animals.
   多环芳香烃也被称为PAHs，指的是一类对人类和动物有毒的化学物质。
3. 3. Polycyclic aromatic hydrocarbons are often found in fossil fuels, such as coal and oil, and their presence has been linked to environmental pollution and human health issues.
   多环芳香烃通常存在于化石燃料中，如煤炭和石油，其存在与环境污染和人类健康问题有关。