These incidents are rare now due to modern occupational safety and health practices. Studies in the s and others conducted after World War II found higher rates of respiratory cancers in these workers. A complicating factor in the post-war studies is that those workers- unlike the workers of the s — included a very large fraction of lifelong cigarette smokers.
That made it more difficult to determine whether it was exposure to cigarette smoke or to chromium that was related to higher rates of lung cancer. Analysis of the workplace studies indicates that prior to the s workers exposed to high levels of chromium had four times the risk of developing lung cancer compared to unexposed people.
Cigarette smoking has been shown to synergistically increase the risk of lung cancer for people exposed to certain metals, such as arsenic, cadmium and nickel as well as other chemicals.
That is, the risk of lung cancer in a smoker exposed to one of these agents is much higher than what would be predicted by simply adding the two individual risks together.
But recent studies suggest that, unlike the case with these and many other lung carcinogen combinations, chromium and cigarette smoking do not act synergistically with each other. The reason for this is not clear, but this supports the idea that chromium is a relatively weak carcinogen even at very high occupational doses. Recent studies indicate that people who began working in chromium industries from the s on under more modern occupational hygiene conditions have levels of respiratory cancer that are not significantly different than the general population.
For example, there are sites in the U. This led to concern over whether area residents were at risk of disease from inhaling chromium-contaminated dusts from these sites.
However, studies comparing the health of residents near these sites to other populations have found no significant differences. Under these conditions, levels of exposure to chromium are likely to be below those of concern.
However, the issue is still under active investigation. Concerns have also been raised about possible health effects of chromium-contaminated drinking water. However, there is no evidence to date of a link between chromium exposure from drinking water and any human health effects. In fact, on a gram-for-gram basis, chromium is not considered particularly toxic as compared to other metals, even by ingestion.
Mutations in certain cancer-associated genes of the cell are believed to be the basis for initiating cancer. How to explain this apparent paradox? During metabolism, chromium passes through several forms that are highly reactive and unstable.
In addition, the process of chromium reduction can create reactive oxygen and other free radicals inside the cell. This combination of reactive intermediates was postulated to be able to attack DNA, leading to the DNA damage and the chromium binding that was observed.
The Wetterhahn uptake-reduction model has served as the central paradigm for the chromium field for the past 20 years, and set the stage for a more complete understanding of how chromium behaves in the body. In cell culture, serum is normally added to help feed cells. This meant no uptake of the chromium, and no DNA damage or mutations.
First, to produce a relatively small number of mutations researchers needed to use chromium levels that are hundreds or thousands of times higher than the levels required by other agents. Second, there appears to be a long latency time for the development of cancer in chromium-exposed workers, requiring as much as 30 to 40 years of exposure.
It also appears that continuous exposure is required, since shorter or disrupted occupational exposures did not significantly increase cancer risk. These observations suggest that chromium might be acting by a mechanism other than, or in addition to causing mutations.
Another class of chemicals that can increase cancer risk slightly without causing mutations are tumor promoters. These agents push a cell along the path of cancer development by acting on mutations caused by other events. To effect cancer rates, tumor promoters also require a constant rather than single or short duration exposure. It has recently been shown that treating cells with chromium causes certain cell signaling changes that are more similar to the effects of tumor promoters than to the effects of mutagens.
The most important chromium compounds are the chromates of sodium and potassium, the dichromates, and potassium and ammonium chrome alums, according to the Los Alamos National Laboratory. Chromium compounds are toxic and should be handled with care. Chromium compounds are all vividly colored and are used as pigments — bright green, yellow, red and orange.
Rubies are red because of chromium, and glass treated with chromium has an emerald green color, according to the Royal Society of Chemistry RSC. Using a technique called electroplating, a thin layer of chromium can coat metal and plastic objects, including car parts and household appliances, to give a shiny, attractive finish. For example, automotive designers use chrome rims and wheels to spruce up their cars. Chrome plating is not only used for looks; because the chromium forms a protective oxide layer on the surface, chrome-plated objects resist corrosion, according to Krebs.
Stainless steel is an alloy of iron and at least It is highly resistant to corrosion. It is used in kitchen cutlery, appliances and cookware such as stainless steel pans and skillets. About 90 percent of leather is chrome tanned, according to Emsley. During this process, chromium sulfate is used to treat animal skin and turn it into leather that is resistant to hot water that can cause degradation.
Kilns and furnaces use bricks made of chromite ore, which retains strength at high temperatures. The textile industry uses chromium ions to help adhere dyes to fabric. Chromium waste slag containing potentially hazardous levels of Cr VI compounds was used as fill material at more than residential, industrial, and recreational sites. Persons living or working in the vicinity of the sites may have been exposed through inhalation, ingestion, or skin contact with contaminated soils and dusts [Fagliano, Savrin et al.
Community exposure from this fill occurred in a variety of ways. Wind erosion of the soil could have made slag particles airborne, increasing the opportunity for inhalation of chromium. Chromium compounds leached by rainwater could have migrated through cracks in soil, asphalt roadways, and masonry walls, forming high-content chromium crystals on their surfaces.
In soil and roadways, these particles might have been eroded by wind and foot traffic and carried as chromium-laden dust into homes and workplaces. Other environmental sources of chromium are cement-producing plants cement contains chromium , the wearing down of asbestos linings that contain chromium, emissions of chromium-based automotive catalytic converters, and tobacco smoke.
The general population is exposed to chromium by eating food or food supplements, drinking water, and inhaling air that contain chromium. One study found increased blood chromium level after total hip replacement using metal-metal pairings where metal ions of the alloys are released [Schaffer, Pilger et al. Skip directly to site content Skip directly to page options Skip directly to A-Z link.
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