Legal Authority for Mosquito Control and Pesticide Use in the United States

Mosquito-borne diseases are a threat globally and in the United States. ^1,2 For instance, in the United States, the West Nile virus first appeared in 1999 and has since spread throughout the country, causing >43 937 cases as of 2015. ³ Recently, 2 other mosquito-borne diseases, dengue virus and chikungunya virus, were locally transmitted in the continental United States for the first time. ^{4 –7} Now, with the increase in Zika virus transmission—including 4752 travel-associated cases and 220 locally acquired cases in the United States as of February 7, 2017—public health officials face the challenge of instituting effective mosquito control programs and making decisions about pesticide use. ^8,9

One question confronting public health officials is this: who has the legal authority for mosquito control in the United States, particularly for pesticide use and regulation? Is it the states or the federal government? The answer to this question is rooted in federalism, the scheme by which the legal authority is divided between the states and the federal government. By the earliest days of English colonial government in America, the colonies had inherited from the English King in Parliament their police powers, the natural plenary power of a sovereign state to regulate private interests for the public good, usually toward defending the health and welfare of their populations. When the Articles of Confederation were formed in 1781, the states were reluctant to give too many of these powers to a national government; thus, they retained individual authority to regulate all issues, except for a very few, including declaring war, trying pirates for crimes committed at sea, and conducting foreign policy and commerce. When the states met at the Constitutional Convention in 1787 to amend and improve the articles, they decided that a new national government was needed. The states ceded more authorities to the national government, and these authorities were expressly enumerated in article 1, section 8, of the US Constitution. These enumerated powers include, among others, the authority to raise taxes and regulate interstate commerce. The states retained all of the authority that they held prior to the US Constitution that was not expressly enumerated to the federal government. Later, in 1791, the Tenth Amendment to the Constitution recognized this reservation of authority: “The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.” ¹⁰

The US Supreme Court, in Jacobson v Massachusetts in 1905, reiterated that the states’ police powers include public health, holding, under a theory of self-defense, that “a community has the right to protect itself against an epidemic of disease.” ¹¹ As a result, states generally have the primary authority to address public health matters within their own borders, ¹² including the authority to control mosquito-borne diseases.

States have a long history of intervening to control mosquito-borne diseases, beginning with outbreaks of yellow fever and malaria, and courts have supported their legal power to do so. In Paris v City of Philadelphia, the court acknowledged that “one of the most unfailing and prolific means of transmitting infectious diseases is in the development of larva, flies, mosquitoes and other disease-bearing insects” and that “it is only by rigid inspection of premises, and enforced hygienic regulation that these dangers can be controlled and minimized.” ¹³

Current State Public Health Authority and Mosquito Control, Including Pesticide Use

Many state and local jurisdictions have laws, including statutes, regulations, and ordinances, in place to protect against the threat of mosquito-borne disease. Some of these laws establish state or local mosquito control programs and set forth goals for these programs, including the reduction of mosquito breeding grounds, removal or treatment of tires, management of solid waste, surveillance, reporting, and outreach and education. ^{14 –20} In addition, state and local laws may regulate pesticide use, including regulating the use of insecticides, larvicides, and adulticides, and might also involve the licensing of applicators and limiting allowable levels of discharge. ^{21 –27}

Mosquito control laws exist at the state and local levels. Variation exists from state to state on whether state or local governments have primary control over needed interventions. In some states, it is the state government that has the primary authority over mosquito control, including pesticide use. For example, in Delaware, state law stipulates that the Department of Natural Resources and Environmental Control may “take all necessary and proper steps and measures for the eradication of mosquitoes,” including “the application of insecticides by air or ground to control immature or adult mosquitoes” to provide “nuisance relief, to protect public health, and to help avoid adverse impacts to local economies from severe mosquito infestations.” ²⁸

In the context of a public health response, a state’s constitution or a state statute may also grant local governments the authority to respond to threats. For example, under Florida law, the time of application and the type of pesticides that may be used are set by a state law, whereas local mosquito control agencies have the authority to apply adulticides by aircraft. ²⁹

Federal Government Authority Over Mosquito Control, Including Pesticide Use

Under their police powers, states have the primary authority to take measures to prevent the spread of mosquito-borne disease within their borders. The US Department of Health and Human Services and its agencies primarily provide support and recommendations. ³⁰ For example, the Centers for Disease Control and Prevention (CDC) coordinates surveillance of mosquito-borne diseases and issues grants to states to facilitate coordination of mosquito control programs at the state and local levels. ^31,32 However, some state actions may also be governed by federal law. These laws generally rest on the federal government’s power to regulate commerce among the states, as found in article 1 of the Constitution. For example, under federal law, CDC can take action if there is a threat that a communicable disease may be introduced or spread either from a foreign country into the United States or from state to state. CDC may also take action as reasonably necessary within a state if it determines that the state or local response is inadequate to prevent spread of the communicable disease from one state to another. Such actions may include mosquito control. ^{33 –37} State and local governments retain the authority to institute mosquito controls in such circumstances, provided that such controls do not conflict with the exercise of federal authority.

The US Environmental Protection Agency, under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), has authority to regulate the labeling, registration, and sale of pesticides, as well as the certification of applicators of restricted-use pesticides. ^38,39 The agency also has authority under the Clean Water Act to set limits on the allowable levels of pesticide discharge into water from pesticide applicators. ^40,41 State and local governments are permitted to use pesticides so long as they are a “federally registered pesticide or device” and use is not otherwise prohibited by FIFRA or other federal law. ⁴²

In Wisconsin Public Intervenor v Mortier, the US Supreme Court reinforced state and local authority, holding that FIFRA did not prohibit state or local pesticide use when adopted “pursuant to its statutory police power.” ⁴³ Since this case, other cases have been filed by individuals in state and federal courts to challenge the state’s use of pesticides; however, these challenges rest primarily on arguments that the pesticide programs violated laws such as FIFRA and the Clean Water Act. These cases do not argue against the state’s authority to institute pesticide regulation or a vector control program. ^{44 –50} As supported by laws and court cases, the decision about whether to use pesticides for public health purposes lies with state or local governments.

Implications for Public Health Law and Practice

Under our system of federalism, as affirmed by the Tenth Amendment, states retain authorities not otherwise delegated to the federal government, including the power to protect the public’s health, welfare, and safety. As a result, states and their localities generally have primary authority to engage in mosquito control within their own borders to protect the public’s health. Primary authority to engage in mosquito control can and, in many states, does include the regulation of pesticide use, application, and licensing, including aerial spraying. Although states have broad authority to protect the public’s health, they still must comply with federal standards established by laws such as FIFRA and the Clean Water Act. Furthermore, if there is a risk of transmission or spread of disease from abroad, from state to state, or, in some circumstances, within the state, CDC can institute additional or different mosquito control efforts, including pesticide use. Ultimately, mosquito control is an important example of how the federal, state, and local governments share authority to respond to a public health threat.