United States Prevention, Pesticides EPA-738-F-94-030 Environmental Protection And Toxic Substances September 1994 Agency (7508W)

R.E.D. FACTS Limonene

Pesticide Reregistration

All pesticides sold or distributed in the United States must be registered by EPA, based on scientific studies showing that they can be used without posing unreasonable risks to people or the environment. Because of advances in scientific knowledge, the law requires that pesticides which were first registered years ago be reregistered to ensure that they meet today\'s more stringent standards.

In evaluating pesticides for reregistration, EPA obtains and reviews a complete set of studies from pesticide producers, describing the human health and environmental effects of each pesticide. The Agency imposes any regulatory controls that are needed to effectively manage each pesticide\'s risks. EPA then reregisters pesticides that can be used without posing unreasonable risks to human health or the environment.

When a pesticide is eligible for reregistration, EPA announces this and explains why in a Reregistration Eligibility Decision (RED) document. This fact sheet summarizes the information in the RED document for reregistration case 3083, limonene.

Use Profile

Limonene is a naturally occurring chemical which is used in many food products, soaps and perfumes for its lemon-like flavor and odor. Limonene also is a registered active ingredient in 15 pesticide products used as insecticides, insect repellents, and dog and cat repellents.

Pesticide products containing limonene are used for flea and tick control on pets, as an insecticide spray, an outdoor dog and cat repellent, a fly repellent tablecloth, a mosquito larvicide, and an insect repellent for use on humans. Formulations include ready-to-use solutions, emulsifiable concentrates, granulars and impregnated material. Limonene is applied by hand as needed, both indoors and outdoors. Use practice limitations include a label prohibition against use on weanling kittens and a caution against use of undiluted product.

Regulatory History

Limonene was first registered as a insecticide in the U.S. in 1958. It was registered as an antimicrobial in 1971, and as a dog and cat repellent in 1983. In May 1988, EPA announced that limonene is considered an inert rather than an active ingredient when used in antimicrobial products (please see 40 CFR 153.139(a)). In April 1994, limonene was granted an exemption from the requirement of a tolerance (or maximum residue limit) when it is an inert ingredient used as a solvent or fragrance in pesticide formulations (please see 40 CFR 180.1001(c), (e)). The Food and Drug Administration (FDA) lists limonene as Generally Recognized as Safe (GRAS) as a food additive or flavoring and a fragrance additive (please see 21 CFR 182.60). Currently, 15 limonene pesticide products are registered.

Human Health Assessment

Limonene is among those pesticide active ingredients for which a reduced set of generic data requirements is appropriate for registration or reregistration. Limonene is naturally occurring, has been established as an inert, is exempt from the requirement of a tolerance, and is recognized as safe by FDA. Its effects are well known and documented in scientific literature; additional testing would not likely provide any new findings. Adequate information is available to characterize its risks to humans and animals.


Limonene is of relatively low acute toxicity taken orally. It is a dermal irritant when applied at high concentrations and may cause dermal sensitization. A 90-day dermal toxicity study using the formulated product is required as confirmatory data to support reregistration of the insect repellent that is to be applied directly to human skin.

A subchronic study by the National Toxicology Program (NTP) using rats and mice resulted in decreased body weights, kidney disease and mortality at the highest dose tested. A chronic toxicity study by NTP using rats resulted in decreased body weight, kidney disease and kidney tumors, which occurred due to a species-specific mechanism. Limonene is not considered a human carcinogen, a developmental toxicant or mutagenic.

Dietary Exposure

Limonene occurs naturally in citrus and other fruits, vegetables, meats and spices. It also is used in a variety of foods and beverages (as well as in soaps and perfumes) to add lemon-like flavor and aroma. FDA considers limonene Generally Recognized as Safe (GRAS) as a food additive or flavoring, and as a fragrance additive. EPA has granted limonene an exemption from the requirement of a tolerance when it is used as an inert ingredient in