1,4-Dichlorobenzene is a chemical used to control moths, molds, and mildew, and to deodorize restrooms and waste containers. It is also called para-DCB or p-DCB. Other names include Paramoth, para crystals, and paracide reflecting its widespread use to kill moths.

At room temperature, p-DCB is a white or colorless solid with a strong, pungent odor. When exposed to air, it slowly changes from a solid to a vapor. It is the vapor that acts as a deodorizer or insect killer.

Most people recognize the odor as the smell of mothballs, and can smell p-DCB in the air at very low levels. Most p-DCB in our environment comes from its use in moth repellent products and in toilet deodorizer blocks.

Structural diagram: National Institutes of Health

Fate & Transport

In air, it breaks down to harmless products in about a month.

It does not dissolve easily in water.

It evaporates easily from water and soil, so most is found in the air.

It is not easily broken down by soil organisms.

It is taken up and retained by plants and fish.

Exposure Pathways

Breathing indoor air in public restrooms and homes that use p-DCB as a deodorizer

Breathing air around some mothballs (check the label)

Breathing workplace air where p-DCB is manufactured

Drinking contaminated water around hazardous waste sites

Eating foods such as pork, chicken, and eggs that are contaminated with p-DCB from its use as an odor control product in animal stalls

Eating fish from contaminated waters

Infants can be exposed by drinking human breast milk from mothers exposed to p-DCB

Health Effects

There is no evidence that moderate use of common household products that contain p-DCB will result in harmful effects to your health. Harmful effects, however, may occur from high exposures. Very high usage of p-DCB products in the home can result in dizziness, headaches, and liver problems. Some of the patients who developed these symptoms had been using the products for months or even years after they first began to feel ill.

Workers breathing high levels of p-DCB (1,000 times more than levels in deodorized rooms) have reported painful irritation of the nose and eyes. There are cases of people who have eaten p-DCB products regularly for months to years because of the sweet taste. These people had skin blotches and lower numbers of red blood cells.

There is no direct evidence that p-DCB can cause birth defects or affect reproduction in humans. Animal studies indicate that breathing or eating p-DCB can harm the liver, kidney, and blood. We have no studies on the health effects from skin contact with p-DCB.

The Department of Health and Human Services (DHHS) has determined that p-DCB may reasonably be anticipated to be a carcinogen. There is no direct evidence that p-DCB can cause cancer in humans, however, animals given very high amounts in water developed liver and kidney tumors.

Information excerpted from:

Toxicological Profile for 1,4-Dichlorobenzene 1993

Agency for Toxic Substances and Disease Registry
U.S. Dept. of Health and Human Services