Nitrogen

Some compounds of nitrogen have been implicated in a variety of environmental questions. For example, sodium nitrate and sodium nitrite have been used as food additives because of their ability to inhibit the growth of disease-causing microorganisms. The compounds are most widely used in preserving meats such as bacon, ham, sausage, hot dogs, and bologna, as well as some fish products.

However, questions have been raised about the possible effects of these additives on human health. Nitrites, for example, appear to decrease the ability of a young child's blood to carry oxygen. In addition, nitrites combine with organic compounds known as amines to form a family of toxic compounds known as the nitrosoamines. These hazards have prompted some scientists and nonscientists alike to call for the ban of nitrates and nitrites as food additives.

Oxides of nitrogen are also involved in problems of air pollution. Although oxygen and nitrogen do not combine with each other at room temperature, they do react at elevated temperatures, such as those produced by an internal combustion engine. As a motor vehicle is operated, nitric oxide is constantly being produced. This oxide, however, readily reacts with oxygen in the air to form nitrogen dioxide, a reddish-brown toxic gas. The tan color that is sometimes associated with smog in urban areas is caused by the presence of nitrogen dioxide. Since nitrogen dioxide is harmful to humans and other animals at low concentrations and toxic at higher levels, its presence in polluted air is a serious environmental issue.