A comparison of air quality standards of the USA and the USSR shows that each country lists about 500 substances for industrial air, but that there is some difference in which pollutants are of concern. Also, limiting values for the same substance tend to differ; in general, USSR standards are lower, both for community air and industrial air. The USA has both primary and secondary standards for some substances; the primary deals with health protection and the secondary (which are more stringent), with protection of the environment. As for industrial air of other nations, non-communist countries have in general adopted the standards of the USA; and communist countries have in general adopted standards intermediate between those of the USSR and the USA. Community standards are much more stringent than those for industry, reflecting, among other factors, the greater margin of safety required for the population at large. Substances for which there are such differences include carbon-monoxide (630080), sulfur-dioxide (7446095), nitrogen-dioxide (10102440), hydrocarbons, ozone (10028156), particulates, and lead (7439921).