The study, which appeared in the journal Nature, also said the pollution caused about 14 million cases of childhood asthma every year.

这项发表在《自然》杂志上的研究还指出，污染每年导致约1400万儿童哮喘病例。

In general, causes of childhood asthma diagnosed before age 12 are thought to be due to a stronger genetic influence, whereas later onset asthma is more likely to be largely due to environmental factors.

一般来说，12岁之前被诊断出哮喘的原因被认为是遗传因素影响更大，而后来的哮喘发作更可能是环境因素造成的。