Description

A naturally occurring oil in citrus peels, dill, fennel, celery and other plants, d-limonene is present in foods and in many essential oils. It can also be synthetically produced. D-limonene is extensively used as a food additive to provide a citrus flavor, as a fragrance in perfumes, air fresheners, in flea control products and personal care products, and as a natural replacement for petroleum-based solvents in paints and cleaning products. D-limonene may also be used as an inert ingredient in pesticides.

Children may inhale its fumes when these products are used indoors, or they may ingest d-limonene in citrus flavored foods.

The EPA lists it as a volatile organic compound, so it can be irritating to anyone who is sensitive.

Though cited as a cancer-causing substance by some, it is still unclear whether this is true. However, fumes containing d-limonene may irritate the eyes and airways of some people, especially when fumes build up indoors.

Health Effects

Immediate Health Effects

If SWALLOWED, d-limonene is Moderately Toxic
If ABSORBED THROUGH SKIN, d-limonene is Not Available
If INHALED (SNIFFED OR BREATHED IN), d-limonene is Not Available

Longterm or Delayed Health Effects

This chemical is considered an Unclassifiable Carcinogen by the World Health Organization, the U.S. Environmental Protection Agency, or another agency.

Other

May be irritating to skin, eye, or airways.
Can trigger allergies in those susceptible.
In laboratory animals, d-limonene has caused kidney tumors in male rats but not in female rats or mice of either gender. The mechanism by which d-limonene caused the tumors in male rats has been determined to be irrelevant to humans, however.
In laboratory animals exposed to high doses in the womb, d-limonene has delayed growth and caused skeletal abnormalities.
Limonene can react with ozone, forming particulates that could impact asthmatics and those with other respiratory ailments.

How Exposures Occur

From food

D-limonene is a natural component of citrus fruits, celery and some spices and as a flavor additive in some foods, beverages and chewing gum. The levels found are usually small quantities.

Inhalation

Children may breathe fumes when products containing d-limonene, such as citrus-scented air fresheners, perfumes and candles, cleaners and paints, are used indoors, especially without adequate ventilation.

Through the skin

D-limonene can be absorbed through the skin after application of citrus essential oils, perfumes, soaps and other fragranced personal care products, and through skin contact with citrus-based cleaning
products.

Significant Statistics

In a 1991 test of 31 fragranced perfumes, soaps, and deodorants, limonene was found in over half.

Fisher, Brandy E. Scents and Sensitivity, Environmental Health Perspectives, Vol. 106 (December 12, 1998), pp. 106-112.http://ehpnet1.niehs.nih.gov/docs/1998/106-12/focus.html

Humans are estimated to consume 0.1 milligram of d-limonene per kilogram of body weight each day.

Phiipsson, A Faulk, Dr., et al. Concise International Chemical Assessment Document on Limonene (No. 5). World Health Organization, International Programme on Chemical Safety, 1998.

Recent research has found that air purifiers can increase the particulate matter in a room when used in the presence of d-limonene.

Burton A 2007. Indoor Air Quality: Lemon-Fresh Ozone. Environ Health Perspect 115:A350-A350. doi:10.1289/ehp.115-a350b. http://ehsehplp03.niehs.nih.gov/article/fetchArticle.action?articleURI=info:doi/10.1289/ehp.115-a350b.

d-Limonene is an active ingredient in 15 registered pesticides. It is considered an inert ingredient if it is used in antimicrobial products.

Reregistration Eligibility Decision: Limonene. US Environmental Protection Agency. September 1994. http://www.epa.gov/pesticides/reregistration/REDs/3083.pdf

Solutions

How to detect d-limonene

Any citrus-based cleaning product, air freshener, perfume, essential oil or fragrance product is likely to contain d-limonene, particularly those that list oil of orange as an ingredient. For more on fragrances in household products, see Fragrances: What Your Nose Needs to Know.

How to minimize exposure to d-limonene

Ventilate well when using products that contain d-limonene or those with strong citrus odor. Some children may be bothered by the fumes, so keep them away.

Alternatives

Use natural deoderizers, such as baking soda, to absorb odors rather than masking them with fragrance-based air fresheners. See Freshen Indoor Air Naturally.
Instead of spraying air fresheners to block odors, improve indoor air quality with good ventilation.

For More information

Books, articles, factsheets and reports

Raloff, Janet. Lemon-scented Products Spawn Pollutants, Science News,Vol. 158, No. 24 (December 9, 2000).

Other government agencies

National Toxicology Program

National Institute for Environmental Health Sciences
P.O.Box 12233
Research Triangle Park, NC 27709
919-541-3345

http://www.niehs.nih.gov

Environmental Protection Agency

Ariel Rios Building
1200 Pennsylvania Avenue, N.W.
Washington, DC 20460
(202) 272-0167
http://www.epa.gov/

Nonprofit organizations

Other websites

International Agency for Research on Cancer, World Health Organization

http://www.iarc.fr

US Department of Health and Human Services
Household Products Database
http://householdproducts.nlm.nih.gov/

Other

Limonene can react with ozone, forming particulates. It is unlikely that levels would rise to levels that might trigger asthma.

In Florida, D-limonene is regulated as an air pollutant when released from citrus processing plants, because it can combine with nitrous oxide to form ozone, contributing to smog, on hot days. The state introduced a trading system that gives credit to emitters who exceed the emissions standard and allows them to sell the credit to emitters who do not meet the standard.

http://www.dep.state.fl.us/secretary/info/pubs/brochure.pdf