Cadmium and other metals

At a Glance

Cadmium is a metal that enters the bloodstream via food, drinking water, and air. It is most often used in batteries, coatings and plating, semi-conductors, and as a stabilizer for plastics. Cadmium has been shown to demonstrate estrogen-like activity, which is known to increase breast cancer risk. Other metals such as nickel, chromium, zinc, lead and mercury have been shown to have similar estrogen-like effects. Cadmium has been recognized as a human carcinogen by both the International Agency for Research on Cancer (IARC) and the National Toxicology Program.

What is cadmium?

Cadmium naturally occurs in the Earth’s crust, and is found in materials extracted from the earth, including metals such as zinc, lead and iron, and fossil fuels such as coal, oil and natural gas.[1] Most cadmium that is produced today comes from the process of mining and refining zinc, and from recycled nickel-cadmium batteries.[2] In 2011, the U.S. production of cadmium was estimated to be 600 metric tons.

Where is cadmium found?

Cadmium is usually found in zinc ore, but also in the mineral greenockite. Cadmium is used in batteries, photocopying, mirrors, vacuum tubes, lubricants, fungicides, glass coloring, paint and nuclear reactors.[3] Cadmium can also be found in smoke detectors and cooking materials that contain Teflon.[4]

Cadmium in soil and water can transfer to the food chain. It has been found in foods such as shellfish, grains, leafy vegetables, and liver and kidney meats. It is also found in tobacco smoke.[5],[6]

What evidence links cadmium to breast cancer?

Researchers have found that there are higher concentrations of nickel, chromium, zinc, mercury, lead and cadmium in cancerous breast tissue when compared with noncancerous tissue.[7] Another study found higher concentrations in blood serum samples of many of these same metals in women diagnosed with breast cancer.[8] Higher cadmium levels in urine[9] and blood have been associated with increased breast cancer risk.[10]

Studies found a statistically significant relationship between dietary consumption of cadmium and later diagnosis of uterine cancers[11] and post-menopausal breast cancers.[12] Other studies have been inconclusive.[13],[14]

Laboratory studies have shown that a number of metals including copper, cobalt, nickel, lead, mercury, chromium and cadmium act like the hormone estrogen, by increasing cell proliferation of breast cancer cells in vitro.[15],[16],[17] Cadmium has been shown to possess the highest level of estrogenic activity.[18]

In animal trials, low doses of cadmium led to an increase in branching and bud formation in mammary tissue. Offspring of rats exposed to cadmium experienced early onset of puberty.[19] These are both factors which are known to increase the risk of breast cancer later in life.

Who is most likely to be exposed to cadmium?

According to the United States Department of Labor, an estimated 300,000 workers are exposed to cadmium in the United States alone.[20] This is most likely to occur in the manufacturing and construction industries, but the expanding nickel-cadmium battery recycling industry is also a cause for concern.

The main industries of concern are those that smelt and refine metals, and those that create batteries, plastics, coatings and solar panels. Recycling and landfill operations are also at risk as workers are potentially exposed to products containing cadmium as well as dust and incineration waste from recycling procedures.

Individuals who smoke will inhale cadmium and because only a small fraction of inhaled or ingested cadmium leaves the body, the concentrations of cadmium in the body grows over time. [21]

Who is most vulnerable to the health effects?

Consumers of shellfish, grains, leafy vegetables, and liver and kidney meats.

Women in their reproductive years are most vulnerable to metals that mimic estradiol.[22] Fetuses are especially vulnerable to the effects of cadmium as it can be transferred through the placenta.[23]  Children are also vulnerable as heavy metals build up in the body over time.[24]

What are the top tips to avoid exposure?

  • Wear appropriate personal protective equipment, including protective clothing and breathing masks, when working in metal, plastic, or waste management fields.
  • Avoid nickel-cadmium batteries and dispose of them safely.

[1] IARC: International Agency for Research on Cancer. Cadmium and Cadmium Compounds. Available online: https://monographs.iarc.fr/ENG/Monographs/vol100C/mono100C-8.pdf (Retrieved July, 2016).

[2] United states department of labor. Occupational safety and health administration. Cadmium. Available online: https://www.osha.gov/SLTC/cadmium/  Retrieved July, 2016).

[3] NTP: National Toxicology Program. Cadmium and Cadmium Compounds. Available online: https://ntp.niehs.nih.gov/ntp/roc/content/profiles/cadmium.pdf

[4] NTP: National Toxicology Program. Cadmium and Cadmium Compounds. Available online: https://ntp.niehs.nih.gov/ntp/roc/content/profiles/cadmium.pdf (Retrieved July, 2016).

[5] NIH: Natational Institute of Health. Tox town. Cadmium. Available online: https://toxtown.nlm.nih.gov/text_version/chemicals.php?id=63  (Retrieved July, 2016).

[6] McElroy, J. A., Shafer, M. M., Trentham-Dietz, A., Hampton, J. M., & Newcomb, P. A. (2006). Cadmium exposure and breast cancer risk. J Nat Cancer Inst, 98(12), 869–873.

[7] Ionescu JG, Novotny J, Stejskal V, et al. (2006). Increased levels of transition metals in breast cancer tissue. Neuroendocrinology Lett, 27 (Suppl 1):36-39.

[8] Wu, H., Chou, S., Chen, D., & Kuo, H. (2006). Differentiation of serum levels of trace elements in normal and malignant breast patients. Biol Trace Elem Res, 113, 9–18.

[9] McElroy, J. A., Shafer, M. M., Trentham-Dietz, A., Hampton, J. M., & Newcomb, P. A. (2006). Cadmium exposure and breast cancer risk. J Nat Cancer Inst, 98(12), 869–873.

[10] Saleh, F., Behbehani, A., Asfar, S., Khan, I., & Ibrahim, G. (2011). Abnormal blood levels of trace elements and metals, DNA damage, and breast cancer in the state of Kuwait. Biol Trace Elem Rese, 141(1-3), 96–109.

[11] Åkesson, A., Julin, B., & Wolk, A. (2008). Long-term dietary cadmium intake and postmenopausal endometrial cancer incidence: A population-based prospective cohort study. Cancer Res, 68(15), 6435–6441.

[12] Julin, B., Wolk, A., Bergkvist, L., Bottai, M., & Åkesson, A. (2012). Dietary cadmium exposure and risk of postmenopausal breast cancer. Toxicology Letters, 211. doi:10.1016/j.toxlet.2012.03.158

[13] Sawada, N., Iwasaki, M., Inoue, M., Takachi, R., Sasazuki, S., Yamaji, T., … Tsugane, S. (2012). Long-term dietary cadmium intake and cancer incidence. Epidemiology, 23(3), 368–376.

[14] Adams, S. V., Newcomb, P. A., & White, E. (2012). Dietary cadmium and risk of invasive postmenopausal breast cancer in the VITAL cohort. Cancer Causes & Control Cancer Causes Control, 23(6), 845-854. doi:10.1007/s10552-012-9953-6

[15] Brama, M., Gnessi, L., Basciani, S., Cerulli, N., Politi, L., Spera, G., … Migilaccio, S. (2007). Cadmium induces mitogenic signaling in breast cancer cell by an Eralpha-dependent mechanism. Mol Cell Endocrinol, 264, 102–108.

[16] Martin, M., Reiter, R., Pham, T., Avellanet, Y., Camara, J., Lahm, M., … Stoica, A. (2003). Estrogen-like activity of metals in MCF-7 breast cancer cells. Endocrinology, 144, 2425–2436.

[17] Sukocheva, O., Yang, Y., Gierthy, J., & Seegal, R. (2005). Methyl mercury influences growth-related signaling in MCF-7 breast cancer cells. Environ Toxicol, 20, 32–44.

[18] Choe, S.-Y., Kim, S.-J., Kim, H.-G., Lee, J. H., Choi, Y., Lee, H., & Kim, Y. (2003). Evaluation of estrogenicity of major heavy metals. Sci Total Environ, 312(1-3), 15–21.

[19] Johnson MD, Kenney N, Stoica A, et al. (2003). Cadmium mimics the in vivo effects of estrogen in the uterus and mammary gland. Nat Med, 9:1081-1084.

[20] United states department of labor. Occupational safety and health administration. Cadmium. Available online: https://www.osha.gov/SLTC/cadmium/  Retrieved July, 2016).

[21] McElroy, J. A., Shafer, M. M., Trentham-Dietz, A., Hampton, J. M., & Newcomb, P. A. (2006). Cadmium exposure and breast cancer risk. J Nat Cancer Inst, 98(12), 869–873.

[22] Martin, M., Reiter, R., Pham, T., Avellanet, Y., Camara, J., Lahm, M., … Stoica, A. (2003). Estrogen-like activity of metals in MCF-7 breast cancer cells. Endocrinology, 144, 2425–2436.

Byrne, C., Divekar, S. D., Storchan, G., Parodi, D. A., & Martin, M. (2013). Metals and Breast Cancer. J Mammary Gland Biol Neoplasia, 18, 63-73.

[23]Byrne, C., Divekar, S. D., Storchan, G., Parodi, D. A., & Martin, M. (2013). Metals and Breast Cancer. J Mammary Gland Biol Neoplasia, 18, 63-73.

[24] Reducing Your Exposure to Heavy Metals in Oregon [PDF]. (n.d.). Oregon Department of Human Services.

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