1,4 Dioxane is a molecular substance that presents as a clear liquid that dissolves in water at all concentrations. It is used primarily as a solvent in the manufacture of chemicals and as a laboratory reagent; 1,4 dioxane also has various other uses that take advantage of its solvent properties. 1,4 Dioxane is a trace contaminant of some chemicals used in cosmetics, detergents, and shampoos. However, manufacturers now reduce 1,4 dioxane from these chemicals to low levels before these chemicals are made into products used in the home.
Exposure to 1,4 dioxane
You can be exposed to 1,4 dioxane when you breathe air, eat food, or drink water contaminated with it. However, current levels of 1,4 dioxane in air, drinking water, and food samples are unknown. In the mid 1980s, levels of 1,4 dioxane in outdoor air ranged from 0.1 to 0.4 µg/m³ (or 1-4 10 millionths of a gram of 1,4 dioxane per 1 cubic meter of air). Levels in outdoor air also can be expressed as 0.03-0.11 parts per billion in units of volume (or ppbv). For indoor air, the average concentrations of 1,4 dioxane were 10 times higher than in outdoor air at levels of 4 µg/m³ (or 4 millionths of 1 gram of 1,4 dioxane per 1 cubic meter of air). Levels in indoor air also can be expressed as ppbv. In the 1970s, drinking water sampled in the United States reportedly contained 1 µg/L (1 µg/L is 1 millionth gram of 1,4 dioxane per 1 liter of water or ppb). However, contaminated wells that may have been used as a source of drinking water have been reported to contain 1 mg per liter (1 ppm). 1,4 Dioxane has been detected in food vapors, which suggests that 1,4 dioxane may be a natural ingredient in some foods. Vapors from chicken, meat, tomato, and small shrimp have been reported to contain 1,4 dioxane. However, the amounts of 1,4 dioxane in other foods are not known.
Tap water can contain 1,4 dioxane, so you also can be exposed to 1,4 dioxane during activities such showering, bathing, and laundering. Exposure to 1,4 dioxane in tap water by breathing in during showering or other indoor activities can result in higher exposures to 1,4 dioxane than from drinking water.
Your skin may contact 1,4 dioxane when you use cosmetics, detergents, and shampoos containing 1,4 dioxane. In 1985, the Food and Drug Administration (FDA) requested that manufacturers limit the level of 1,4 dioxane in cosmetic products to levels not greater than 10 milligrams of 1,4 dioxane per kilogram of product (10 mg/kg or 10 ppm). However, during 1992-1997, the average concentration of 1,4 dioxane in some cosmetic products reportedly ranged from 14 to 79 mg/kg.
Pathways for 1,4 dioxane in the body
1,4 Dioxane can enter the body by contact of the skin with products that contain it or with contaminated soil, by breathing vapors that escape from liquids that contain 1,4 dioxane (as may happen when showering with contaminated water), or by eating contaminated food. Studies in volunteers have shown that after inhalation of vapors of 1,4 dioxane, almost all of the 1,4 dioxane that enters the lungs can pass to the blood stream. Studies in animals have shown that the same can occur with 1,4 dioxane that is swallowed and reaches the stomach. Much smaller amounts of 1,4 dioxane can pass to the bloodstream if it contacts your skin. Once in the bloodstream, 1,4 dioxane is distributed throughout the body and is rapidly converted into other chemicals, or metabolites, which quickly leave the body in the urine. Neither 1,4 dioxane nor its metabolites build up in the body.
Health effects of 1,4 dioxane
You should know that one way to learn whether a chemical will harm people is to determine how the body absorbs, uses, and releases the chemical. For some chemicals, animal testing may be necessary. Animal testing may also help identify such health effects as cancer or birth defects. Without laboratory animals, scientists would lose a basic method for getting information needed to make wise decisions that protect public health. Scientists have the responsibility to treat research animals with care and compassion. Scientists must comply with strict animal care guidelines because laws today protect the welfare of research animals.
Additionally, there are vigorous national and international efforts to develop alternatives to animal testing. The efforts focus on both in vitro and in silico approaches and methods. For example, the National Toxicology Program (NTP) at the National Institute of Environmental Health Sciences (NIEHS) created the NTP Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) in 1998. The role of NICEATM is to serve the needs of high quality, credible science by facilitating development and validation—and regulatory and public acceptance—of innovative, revised test methods that reduce, refine, and replace the use of animals in testing while strengthening protection of human health, animal health and welfare, and the environment. In Europe, similar efforts at developing alternatives to animal based testing are taking place under the aegis of the European Centre for the Validation of Alternative Methods (ECVAM).
Few studies are available that provide information about the effects of 1,4 dioxane in humans. Acute accidental exposure to high amounts of vapors of 1,4 dioxane that have caused death in people have been reported. In these cases, skin contact with the chemical also probably occurred. Autopsies of these patients showed extensive damage to the liver and kidneys. Volunteers who breathed controlled low levels of 1,4 dioxane vapors for short periods (minutes to hours) complained of irritation of the eyes and the nose. A few studies of workers exposed to 1,4 dioxane for long periods did not show any significant harmful health effects. Studies in animals have shown that breathing vapors of 1,4 dioxane, swallowing liquid 1,4 dioxane or contaminated drinking water, or having skin contact with liquid 1,4 dioxane also affects mainly the liver and kidneys. Animals that breathed high amounts of 1,4 dioxane also became drowsy. Scientists do not know whether 1,4 dioxane affects reproduction or the ability to fight infections in people or animals. The limited number of studies of workers did not indicate whether 1,4 dioxane causes cancer in humans. However, laboratory rats and mice that drank water containing 1,4 dioxane during most of their lives developed liver cancer; the rats also developed cancer inside the nose. Scientists are debating the degree to which the findings in rats and mice apply to exposure situations commonly encountered by people. On the basis of inadequate evidence in humans and sufficient evidence in experimental animals, the International Agency for Research on Cancer has determined that 1,4 dioxane is possibly carcinogenic to humans. The U.S. Department of Health and Human Services considers 1,4 dioxane as reasonably anticipated to be a human carcinogen on the basis of sufficient evidence of carcinogenicity in experimental animals. The Environmental Protection Agency (EPA) has established that 1,4 dioxane is a probable human carcinogen on the basis of inadequate evidence in people and sufficient evidence in animals. It should be pointed out that the limited environmental monitoring data available suggest that the levels of 1,4 dioxane to which the general population might be exposed through contact or use of consumer products (including food), or that are normally found in environmental media, are generally significantly lower than those used in studies with experimental animals.
Health effects in children
This section discusses potential health problems in people from exposures during conception to maturity (18 years of age).
Children can be exposed to 1,4 dioxane from contaminated air and food, and from drinking contaminated well or tap water; from showering or bathing with contaminated water; and from using consumer products that contain small amounts of 1,4 dioxane; however, based on available measurements, these risks are very low. It should be noted that exposure to 1,4 dioxane by breathing in evaporated contaminated water during showering or other indoor activities can result in higher exposures to 1,4 dioxane compared to drinking the tap water.
Children play outdoors and can be exposed if they touch or eat contaminated soil or place dirty objects in their mouths.
There are no studies of children exposed to 1,4 dioxane. However, children might experience health problems similar to those in adults if they were exposed to high concentrations of 1,4 dioxane. 1,4-Dioxane could harm children's liver and kidneys, depending on the amount of 1,4 dioxane entering the body.
Scientists do not know whether exposure of pregnant women to 1,4 dioxane can harm the unborn child, or if so, what levels of maternal exposure might harm the fetus. Not enough animal studies are available that can help predict what might happen in people. 1,4 Dioxane does not build up in the body, but a nursing mother exposed to a high amount of 1,4 dioxane might pass it to the infant in breast milk. However, scientists do not know whether this occurs in people or animals.
Reducing risk of exposure to 1,4 dioxane
If your doctor finds that you (or a family member) have been exposed to substantial amounts of 1,4 dioxane, ask whether your children also might have been exposed. Your doctor might need to ask your state health department to investigate.
Families that drink water that could be contaminated with 1,4 dioxane can reduce the risk for exposure to 1,4 dioxane by drinking uncontaminated bottled water. Children who live near hazardous waste sites that might be contaminated with 1,4 dioxane should be discouraged from playing in mud and water near these sites because these sites might contain 1,4 dioxane. Children also should be discouraged from eating mud, and they should follow careful hand washing.
1,4 Dioxane may be a contaminant in cosmetics, detergents, and shampoos that contain the following ingredients (which may be listed on the product label): "PEG," "polyethylene," "polyethylene glycol," "polyoxyethylene," "-eth-," or "-oxynol-." Most manufacturers remove 1,4 dioxane from these ingredients to concentrations recommended by the FDA as safe. Thus, most products on the market today contain 1,4 dioxane in very small amounts or not at all. However, some cosmetics, detergents, and shampoos may contain 1,4 dioxane at levels higher than recommended by FDA. Because products contaminated at concentrations higher than the FDA-recommended levels are not possible to determine without testing, families should avoid using products containing the ingredients listed above unless the manufacturer can guarantee that 1,4 dioxane is below the FDA-recommended level.
Medical tests for exposure to 1,4 dioxane
1,4 Dioxane and its breakdown products can be measured in your blood and urine, and positive results indicate you have been exposed to 1,4 dioxane. The tests are not routinely available at your doctor's office because they require special equipment, but the doctor can collect the samples and send them to a special laboratory. The tests need to be conducted within days after the exposure because 1,4 dioxane and its breakdown products leave the body fairly rapidly. These tests do not predict whether exposure to 1,4 dioxane will produce harmful health effects.
- The Agency for Toxic Substances and Disease Registry
- Interagency Coordinating Committee on the Validation of Alternative Methods
- European Centre for the Validation of Alternative Methods
- Institute for Laboratory Animal Research
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