Air Pollutants and Effects Questions and Answers

Answer: B

Depletion of stratospheric ozone causes skin cancer.

The ozone layer absorbs most of the sun's ultraviolet-B radiation. When it thins, more UV-B reaches the ground, and that radiation damages DNA in skin cells, raising the incidence of skin cancers, including melanoma, as well as cataracts and suppression of the immune system.

A rise in CO₂ comes from burning fuels and clearing forests, not from ozone loss. Cholera is a waterborne bacterial disease and dengue a mosquito-borne viral one; neither is caused by ultraviolet exposure.

Answer: A

Asphyxiants exclude oxygen.

Simple asphyxiants are gases that are not themselves very toxic but displace oxygen from the air breathed, so that the body is starved of it. Chemical asphyxiants, such as carbon monoxide and hydrogen cyanide, prevent the body from carrying or using oxygen. Either way, it is oxygen that is kept from the tissues.

Nitrogen, carbon dioxide and methane are themselves common simple asphyxiants in confined spaces such as sewers and silos, so they are what displaces oxygen, not what is excluded.