A country in NORTH AMERICA, bordering the Caribbean Sea and the Gulf of Mexico, between BELIZE and the UNITED STATES, and bordering the North Pacific Ocean, between Guatemala and the UNITED STATES.
D000397
Air Pollution
The presence of contaminants or pollutant substances in the air (AIR POLLUTANTS) that interfere with human health or welfare, or produce other harmful environmental effects. The substances may include GASES; PARTICULATE MATTER; or volatile ORGANIC CHEMICALS.
Air Quality,Air Pollutions,Pollution, Air
D012189
Retrospective Studies
Studies used to test etiologic hypotheses in which inferences about an exposure to putative causal factors are derived from data relating to characteristics of persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or outcome of interest and their characteristics are compared with those of unaffected persons.