Healthy Milk, Healthy Baby
Chemical Pollution and Mother's Milk
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Organic solvents are ubiquitous in both industrial and household settings. These chemicals are used to dissolve other chemicals, and are present in paints, varnishes, thinners, dry-cleaning fluids, some glues, degreasers, and gasoline. Solvents include a wide variety of chemicals with varying properties, defined more by their use than by their chemistry or toxicity. In general, these chemicals are highly volatile, absorbed readily through the skin, and common water contaminants. As a result of their widespread presence in the environment, solvents are found in human urine, exhaled breath, blood, and fat. Because solvents, unlike the Persistent Organic Pollutants (POPs), are relatively short-lived in the body, detection implies recent exposure. Because these chemicals are often fat-loving (lipophilic), there is ample reason for concern that they can get into breast milk.
Numerous organic solvents have been detected in human breast milk, including benzene, chloroform, methylene chloride, styrene, perchloroethylene, toluene, trichloroethylene, 1,1,1-trichloroethane, and xylene. Breast-milk levels of these compounds are frequently higher than blood levels because solvents are fat-loving and because breast tissue does not eliminate solvents as quickly as they are eliminated from blood. Perchloroethylene, in particular, is known to concentrate in breast milk, to levels about three times higher than levels in blood. That said, much of the research on this group of chemicals has been preliminary and is of two types: theoretical models estimating which solvents may get into breast milk, and small monitoring studies on only a few people. Most countries have not conducted studies of solvents in breast milk, and have gathered no data representative of the general population. Due to limited data, it is possible only to conclude that some solvents get into breast milk; no information relevant to the levels of exposure, geographic differences, or time trends can be relied upon.
Health Effects of Solvents
Solvents can have a range of health effects, depending on the individual chemical. In general, solvents can cause acute and chronic neurological symptoms, ranging from headaches to mood changes to short-term memory loss. Solvents are also toxic to the liver, potentially resulting in chemical hepatitis or jaundice. Prenatal exposure to solvents has been linked to miscarriage. Some solvents, such as toluene (found in many glues) can cause birth defects. Other solvents, such as benzene and vinyl chloride, are known to cause cancer, while some others are suspected carcinogens. Only one clear-cut case of an adverse health effect in a breastfeeding infant due to solvent exposure has been reported.
Solvents in the Body
People can be exposed to solvents in many ways in their daily lives. For example, ethyl alcohol is a solvent that can get into breast milk, and many breastfeeding mothers are exposed to it by drinking wine, beer, or other alcoholic beverages. Many occupations involve exposure to this broad class of chemicals, and exposure also occurs in such hobbies as furniture refinishing, oil painting, automotive repair, or any hobby using glues that are not water-based. Other exposures occur from using certain consumer products, especially pesticides and spot removers, or during daily life in the community - at gasoline stations or dry cleaners, for example.
Solvents are also present in air. Indoor air exposures may be related to "off-gassing" from carpets and pressed-wood products in furniture, as well as to gasoline vapors from cars parked in attached garages. Solvents are also relatively common contaminants in drinking water. As a result, most infants probably receive higher solvent exposures from indoor air, water, and reconstituted formula than they do from breast milk.
Controlling Exposure: Bans and Restrictions
No complete bans on solvents are to be found anywhere in the world. Some solvents are restricted, however. For example, the testicular toxicity and miscarriages associated with some of the glycol ethers have spurred efforts to replace these chemicals in many industries. Also, benzene is now restricted to smaller quantities in gasoline in the United States, and many paints are now water-based. These changes have reduced exposure to some solvents among the general population.
Breast-milk Monitoring Studies Measuring Solvents
Because solvents are a widely used group of chemicals that can enter the body and move into fat, some researchers have speculated that they are likely to make their way into breast milk. This speculation has been shown to be correct in certain situations. But unlike the persistent organic pollutants (POPs), solvents are usually removed from the body very rapidly. Exhalation serves as a major route of elimination. As a result, these chemicals are not expected to accumulate over time in breast milk, suggesting a diminished likelihood of exposure throughout lactation, but the potential instead for repeated transient exposures. This same short-lived property makes it easier for lactating women to avoid exposure and thereby to have some degree of control over the likely levels of these chemicals in their milk.
Very few breast milk-monitoring studies have looked for solvents. Their short-lived nature makes sampling particularly challenging, since samples need to be collected and transported in a special way, and analyzed very quickly so that solvents in the sample do not evaporate between the time of collection and the time of analysis. However, in a few studies, a wide range of solvents has been reported in breast milk in various locations (see list below). In most instances, the study population includes very few women. In addition, because of the lack of comprehensive studies, no definitive research has been conducted regarding the relevance and significance of these levels.
Instead, most research regarding solvent exposure in breast milk has come from modeling. These studies have predicted the solvent levels likely to exist in breast milk and have examined the theoretical risks of these levels. Some of these models have been developed in order to investigate whether maternal exposures to solvents in the workplace may pose a risk to a breastfeeding infant. In one modeling study, three solvents were estimated to exceed U.S. EPA's health advisory level for drinking water if exposure occurred at the legally allowable workplace limit. These chemicals were bromochloroethane, perchloroethylene, and 1,4-dioxane. In addition, predicted breast-milk levels of carbon tetrachloride and trichloroethylene were extremely close to the EPA health advisory level. Indeed, these estimates are likely to underestimate potential risk in the workplace because the EPA risk values used were for non-cancer health effects, whereas several of the solvents evaluated are carcinogens. Accounting for this difference would potentially add additional solvents to the list of potential concern, most notably benzene.
Solvents Reported in Breast Milk
Ethyl butyl ketone
Methyl ethyl ketone
Methyl propyl ketone
Some Important Examples of Solvents in Breast Milk
Some evidence indicates that chronic exposure to gasoline vapors may lead to decreased milk production. This is an obvious concern, since duration of lactation is directly related to the positive benefits of breastfeeding. If true, solvent exposure may detract from some of the benefits of breastfeeding.
One case report described a breastfeeding child who developed jaundice, indicative of a toxic effect on the liver. Temporarily halting breastfeeding resulted in resolution of the child's symptoms. The mother reported visiting her husband daily at lunch time at his job with a dry cleaning firm. Monitoring of the woman's breast milk found that she had extremely high levels of perchloroethylene in her milk, probably due to exposure in the shop. Because her exposure was repeated every day, the elimination of perchloroethylene from her body became saturated and as a result, high levels built up in her breast milk. This case probably does not reflect normal-population-level exposure to perchloroethylene; however, it is an important indicator of the potential for adverse effects in cases where exposure is chronic and at significant levels. In addition, a modeling study predicting levels of perchloroethylene in the breast milk of women living in apartments atop dry cleaning shops revealed potential infant exposure from breastfeeding. Of course, these children would also be exposed from breathing the air inside such apartments.
Solvents are an avoidable source of potential chemical exposures. Although very little information has been gathered about these chemicals in breast milk, we do know that many solvents can enter the mother's body and then transfer into her milk. Because use of these chemicals is so widespread, the subject merits further research.
Women concerned about solvent exposures during lactation may take some common sense steps to reduce their exposure. The most important is to avoid drinking alcohol while breastfeeding. Other activities that may reduce exposures include avoiding any hobbies or household activities involving such volatile chemicals as paints, non-water-based glues, and varnishes. Exposures can also occur from pumping gasoline, visiting the dry cleaner, and bringing home dry cleaned clothes. Solvent use in the workplace can also pose an exposure risk. Women who are breastfeeding and exposed to solvents can make an attempt to time their feedings, because the levels of solvent in breast milk declines relatively rapidly over several hours. These exposure-reduction techniques will help protect infants from solvent residues in breast milk, and will also help protect them from exposures to solvents in indoor air and water.
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last revised 5.22.01