Ozone provides a natural protective filter against harmful ultra-violet rays from the sun, which can cause sunburn, cataracts and skin cancer as well as damage vegetation.

臭氧提供天然的保护，防止太阳的有害紫外线的侵害，这种紫外线会导致晒斑，白内障，皮肤癌以及危害植物。

youdao

Scientists thought large, wholly natural, year-to-year variations in Antarctic ozone would obscure any small upward trend.

科学家们过去认为南极洲上大规模臭氧层年际变化会掩盖住微小的趋势。

youdao

The stratosphere holds an natural amount of ozone, but by Earth's surface this becomes air pollution.

大气平流层中存在有大量的臭氧，它们若是在地球表面则会造成空气污染，空气中的臭氧会严重破坏人的肺部。

youdao

Carbon monoxide is exclusively artificial, and though some ozone is the result of natural processes, most of it is not.

ECONOMIST: Saturday-night showers

Natural gas vehicles emit up to 90 percent fewer ozone-depleting gases than gasoline-powered cars.

CNN: Natural gas vehicles on a roll in U.S.