Population at risk: 16 million people
Estimated DALYs: 3 million
Chromium (Cr) is a naturally occurring heavy metal found in the earth’s crust. Although it can be released into the environment through natural processes, it is also released from industrial sources. Chromium is typically found in two forms: chromium III and chromium VI, which are respectively known as trivalent chromium and hexavalent chromium. Trivalent chromium is the most stable of the forms and occurs naturally. In contrast, hexavalent chromium does not occur naturally, and is often the end product of anthropogenic activities.
Industries associated with chromium use include leather tanning operations, metal processing, stainless steel welding, chromate production and chrome pigment production. Chrome uses in tanning is a particular problem, both with the chrome processing plants that supply chrome salts to the tanneries and at tannery complexes that do not have adequate wastewater control and treatment. Due to the relatively inexpensive cost of labor and materials, almost half of the world’s tanning and leather industries are located in low- and middle-income countries (LMICs).1
Pure Earth estimates that 16 million people are at risk for exposure to chromium globally, with an estimated burden of disease of 3 million DALYs. As of 2015, the Toxic Sites Identification Program has identified over 300 sites around the world where exposure to chromium threatens the health of the population.
Pathways & Exposure Routes
Industrial processes and improper management of waste products can result in chromium-contaminated air, water, soil and food. The most common routes of exposure to chromium through these media are ingestion, inhalation and dermal contact with soil, water, or particulates in the air contaminated with chromium. The most common route of exposure in occupational settings is inhalation, which has been linked with a variety of health problems.
Associated Health Effects
Development of adverse health effects resulting from chromium exposure is dependent on the route of exposure and the type of chromium affecting a population.
Of the two forms, hexavalent chromium poses greater health risks due to its higher toxicity and the associated cellular uptake pathways. General health effects from exposure to hexavalent chromium include damage to the gastrointestinal, respiratory and immunological systems, as well as reproductive and developmental problems. Furthermore, hexavalent chromium is a known human carcinogen. Depending on the route of exposure, exposure to hexavalent chromium can increase the rate of various types of cancers. Observations documenting higher lung cancer rates in workers occupationally exposed to chromium date back as far as the 1930s.2 Additionally, the inhalation of chromium may lead to nasal perforation, leaving affected individuals more susceptible to attacks on the respiratory system. Gastrointestinal effects have been associated with ingestion of chromium-contaminated material, with recent studies showing hexavalent chromium to be stomach carcinogen in humans.3
It is important to note that although trivalent chromium has a lower toxicity compared to its hexavalent counterpart, negative health effects can result from trivalent chromium exposure. Studies have shown that chronic exposure to trivalent chromium, particularly in occupational settings, can cause significant damages to lymphocyte DNA. Studies of both chromium compounds have also indicated that chromium accumulation in the human body may have adverse effects on iron metabolism, a critical process for the maintenance of normal bodily functions and an essential component of red blood cells.4 As most of the human body’s iron is contained in red blood cells, iron deficiency anemia may result if the body cannot absorb enough of the metal.5
1 Azom M, Mahmud K, Yahya S, Sontu A, Himon S. Environmental impact assessment of tanneries: A case study of Hazaribagh in Bangladesh. International Journal of Environmental Science and Development. 2012;3(2):152-156
2 Jacobson E. Chromium: A thoroughly modern metal. Dartmouth Toxic Metals Superfund Research Program Web site.http://www.dartmouth.edu/~toxmetal/toxic-metals/more-metals/chromium-history.html. Published 2010. Updated 2010. Accessed October 30, 2015
3 Welling R, Beaumont JJ, Petersen SJ, Alexeeff GV, Steinmaus C. Chromium VI and stomach cancer: A meta-analysis of the current epidemiological evidence. Occup Environ Med. 2015;72(2):151-159
4 Medeiros MG, Rodrigues AS, Batoreu MC, Laires A, Rueff J, Zhitkovich A. Elevated levels of DNA-protein crosslinks and micronuclei in peripheral lymphocytes of tannery workers exposed to trivalent chromium. Mutagenesis. 2003;18(1):19-24
5 Kornhauser C, Wrobel K, Wrobel K, et al. Possible adverse effect of chromium in occupational exposure of tannery workers. Ind Health. 2002;40(2):207-213