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] Another dietary study found that higher dietary intake of cadmium at the start of the study was associated with increased risk for breast cancer over the 22 years of follow-up.  The effect was more pronounced for women who had been premenopausal at the beginning of the study.[13]

Similarly, higher airborne levels of cadmium (as well as mercury and lead) have been associated with higher risk of developing post-menopausal breast cancer.[14] Other studies have been inconclusive.[15],[16]

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.[17],[18],[19] Cadmium has been shown to possess the highest level of estrogenic activity.[20]

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.[21] These are both factors which are known to increase the risk of breast cancer later in life.

What about effects of exposure to cadmium in women who have been diagnosed with breast cancer?

For women living with a diagnosis of breast cancer, higher blood cadmium levels have been associated with earlier distant organ metastases.[22]

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.[23] 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. [24]

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.[25] Fetuses are especially vulnerable to the effects of cadmium as it can be transferred through the placenta.[26]  Children are also vulnerable as heavy metals build up in the body over time.[27]

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.\

Updated 2019