How safe are detergents?
Detergents and cleaning materials are a major group of chemicals to which consumers are exposed every day. Laundry practices have been revolutionized in the past century, washing machines have by and large displaced washing clothes with regular soap, and today’s detergents have gone through several transformations from their original predecessors. Their safety is of the utmost importance, because everybody is exposed daily and continuously.
Some decades ago lye (sodium hydroxide) was used as a detergent when clothes were washed by boiling and then rinsed in a tub. Every year many unattended children would drink a mouthful of concentrated lye from a glass or a bottle lying in the laundry room. This caused oesophageal constrictions which were very difficult to treat surgically. Fortunately such serious accidents are now history. The present risks are much lower: long-term risks or allergies rather than acute risks.
However, some detergents used in dishwashers are still very alkaline, even if not quite as strong as lye. Therefore dishwasher detergents must be kept out of the reach of children. Single-packed tablets are good in this respect since a small child is not very likely to swallow one of these huge tablets.
Laundry detergents were modified in the beginning of 1990s in a very significant way. Phosphates were causing eutrofication of waterways, and so they were largely replaced by zeolites as water softening agents which make water softer by exchanging calcium in the water for sodium. Zeolites are synthetic aluminium silicates somewhat resembling clay. They include a large number of related chemicals, in fact there are more than 100 of them, and some 40 are natural compounds in the environment. Zeolites do not disintegrate during wastewater treatment but settle in the sedimentation basins.
Some zeolite particles remain in the washed laundry. At almost the same time as zeolites were introduced, water-conserving washing machines started to become popular. Thus when clothes, washed with detergents containing zeolites, are being rinsed with tiny volumes of water, the zeolites are not properly removed. This may mean that not only is the washing result poor, but also the consumer is exposed to zeolite particles remaining among the fibres of the fabric. In addition one might ask if zeolites are really any longer needed, because phosphate removal in waste water plants has become much more effective. Depending on the availability of water, in many countries extreme water conservation may not even be necessary or even desirable. Perhaps water-stingy washing machines should be sold in densely populated countries and different models would be available in less populated countries where there is no need to restrict the use of water.
Long term exposure to a variety of silicates has been known for some time now to cause lung fibrosis and other lung diseases. One possible mechanism is the formation of oxygen radicals and the consequent tissue damage. In the lung, the macrophage cells try to "eat" silicate particles and in the process they produce oxygen radicals to destroy (to "burn") the foreign material, but an excess of radicals can also harm the body’s own tissues. Some of the natural zeolites cause cancer, e.g. erionite has been classified a human carcinogen. It is even more potent than crocidolite asbestos. Most of the other zeolites are less carcinogenic.
The zeolite used in detergents is synthetic zeolite A. It has not been found to be toxic in animal experiments. In rats and hamsters, one rather limited experiment using respiratory exposure did reveal the accumulation of zeolite particles in the lungs, in macrophages, as well as in lymph nodes. However, no inflammatory reactions or any increase of connective tissue were seen. This can be interpreted as a reassuring sign that there is no tissue damage or oxygen radical formation. As yet it is not known what the true risk is to human beings. However, since they are another class of fine particulate matter, one should not be surprised if they cause some adverse health effects.
Enzymes are used in detergents to remove organic smudges. They are often made by biotechnological methods using microbes. The most important enzymes in detergents are proteases, lipases, amylases and cellulases. Since all enzymes are proteins, they can be allergenic; usually the allergies are IgE-derived immediate hypersensitivity reactions. The most problematic detergents are powdery substances that form a dust. There are fewer problems with the liquid preparations.
Rinses, softeners, conditioners
Softeners are intended mainly to soften textile fabrics and to decrease static electricity. Hair conditioners in essence do the same. They are not necessary for a good washing result. Rinses may contain many sorts of chemicals, including tensides and fragrances. Softener molecules remain on the surface of the textile fibre, and may cause allergic reactions. All in all, fragrances are the most common cause of allergies in detergents and rinses.
Zeolites in detergents are an example of a change initiated for environmental reasons that would have benefited from collaboration in planning. Detergents, washing machines and wastewater treatment have all apparently developed independently of each other, assuming no changes in the other areas.
Notes and references
- Macrophage cells are specialized in "eating" and destroying foreign materials.
- Tensides are substances decreasing surface tension and removing dirt. They mix both with water and with fat molecules.
One level up: A favourite of children - and some adults too
Previous chapter: Should we have antibiotic chemicals present in everyday domestic items?
Next chapter: Can noise cause true health problems?