Examples are St. Louis encephalitis and La Crosse encephalitis transmitted by mosquitoes and plague and murine typhus transmitted by fleas. Chemical hazards result from mismanagement or misuse of chemicals resulting in an unacceptable risk to human health. Examples of categories of pesticides are herbicides and insecticides. Most pesticides kill non-target organisms as well as the target, or pest species. The wise use of pesticides can protect human health and agricultural crops.
Misuse of pesticides can result in illness and death.
Some of the pesticides developed earlier in the 20 th Century, such as DDT, were persistent, that is they remained in the environment for months or years after their initial use. Newer pesticides are less persistent in the environment. Diseases associated with ETS include lung cancer and perhaps heart disease. The EPA has classified ETS as a Class A carcinogen. Smoking has been increasingly restricted from public buildings and from many private work sites.