Cadmium is a harmful metal that occurs naturally. People may be exposed to it in workplaces, in soil where plants grow, and through smoking. Because the amount of cadmium that is safe for humans is very small, even tiny amounts can be dangerous. Cadmium is widely used in electroplating, but this process usually does not cause too much exposure. It is also found in some industrial paints and can be risky when the paint is sprayed. Removing cadmium paint by scraping or blasting can create a serious hazard. The main use of cadmium is in making NiCd rechargeable batteries. The main source of cadmium comes from refining zinc metal. Rules about exposure to cadmium are included in standards for general industry, shipyard work, construction, and agriculture.

Signs and symptoms

Acute exposure to cadmium fumes can cause symptoms similar to the flu, such as chills, fever, and muscle aches, sometimes called "the cadmium blues." These symptoms may improve within a week if there is no damage to the lungs. More serious exposure can lead to tracheobronchitis, pneumonitis, and pulmonary edema. Symptoms of inflammation may appear hours after exposure and include coughing, dryness and irritation in the nose and throat, headache, dizziness, weakness, fever, chills, and chest pain.

Complications from cadmium poisoning include coughing, anemia, and kidney failure, which can be life-threatening. Exposure to cadmium increases the risk of developing cancer. Like zinc, long-term exposure to cadmium fumes can cause a lifelong loss of the ability to smell.

A major effect of cadmium poisoning is weak and brittle bones. Bones may become soft (osteomalacia), lose mineral density (osteoporosis), and weaken. This can cause joint and back pain and increase the risk of fractures. Spinal and leg pain are common, and a waddling walk may develop due to bone changes from long-term exposure. Pain often becomes severe, and fractures become more likely as bones weaken. Permanent bone deformities can occur. In extreme cases, even body weight can cause a fracture.

Kidney damage caused by cadmium poisoning cannot be reversed. Kidneys may shrink by up to 30%. The kidneys lose the ability to remove acids from the blood, a condition called proximal renal tubular dysfunction. This leads to low phosphate levels in the blood (hypophosphatemia), causing muscle weakness and sometimes coma. High chloride levels (hyperchloremia) also occur. Kidney problems can cause gout, a type of arthritis from uric acid buildup in joints due to high blood acidity (hyperuricemia). Cadmium exposure is also linked to kidney stones.

Sources of exposure

Smoking is an important source of cadmium exposure. Even small amounts of cadmium from smoking are very harmful to humans because the lungs absorb cadmium more easily than the stomach. Cadmium is released into the aerosol from electronic cigarettes (ECs). Based on current data, the lifetime cancer risk (LCR) from this exposure does not go above the acceptable level.

Cadmium has been building up in water, air, and soil, especially in industrial areas. Environmental exposure to cadmium has caused serious health problems in Japan, where people have eaten rice grown in soil contaminated with cadmium from irrigation water. This condition is called itai-itai disease.

People living near hazardous waste sites or factories that release cadmium into the air may be exposed to cadmium in the air. In the United States, many state and federal rules control how much cadmium can be released into the air from waste sites and incinerators, ensuring that properly managed sites are not dangerous. However, the general population and people near unregulated or accidentally contaminated areas may be exposed to cadmium through food, dust, or water. Rules and pollution controls are in place to prevent such releases.

Some phosphate fertilizers contain cadmium at levels up to 100 mg/kg, which can increase cadmium levels in soil, as seen in New Zealand.

Food is another source of cadmium. Plants in non-industrial areas may contain small or moderate amounts of cadmium, but adult animals may have high levels in their livers and kidneys. Daily cadmium intake from food varies by region. In Europe and the United States, intake is about 8 to 30 micrograms per day, while in parts of Japan, it is 59 to 113 micrograms per day. A small study found that 48% of premium dark chocolate samples had high cadmium levels, likely because the soil where the cocoa was grown contained cadmium.

In the 1950s and 1960s, industrial workers were exposed to high levels of cadmium. As the dangers of cadmium became known, limits on exposure were reduced in most industrialized countries. Many leaders now agree that further reductions are needed. When working with cadmium, it is important to use a fume hood to avoid dangerous fumes. Brazing fillers with cadmium must be handled carefully. Long-term exposure to cadmium plating baths has caused serious health issues.

Workers may be exposed to cadmium in the air during metal smelting, refining, or in factories that produce cadmium-based products like batteries, coatings, or plastics. Workers may also be exposed during soldering or welding metal containing cadmium. In the United States, about 512,000 workers are in environments where cadmium exposure may occur each year. Rules set safe exposure levels to protect workers and keep air cadmium levels below harmful levels.

Artists who use cadmium pigments, often found in bright orange, red, and yellow paints, may accidentally ingest dangerous amounts, especially when using dry forms like chalk pastels or mixing their own paints.

Cadmium is used in nickel-cadmium batteries, which are among the most common cadmium-based products.

In May 2006, the sale of seats from Arsenal F.C.’s old stadium, Highbury in London, was canceled after trace amounts of cadmium were found in the seats.

In February 2010, cadmium was discovered in an entire line of Miley Cyrus jewelry sold by Wal-Mart. Tests by the Associated Press found high levels of cadmium in the charms. Wal-Mart did not stop selling the jewelry until May 12 because testing all products on shelves was difficult.

On June 4, 2010, cadmium was found in the paint on promotional drinking glasses for the movie Shrek Forever After, sold by McDonald’s. This led to a recall of 12 million glasses.

Toxicology

Cadmium is a very harmful substance that pollutes the environment and is dangerous to human health. It is classified as a cancer-causing agent by several organizations: Group 1 by the International Agency for Research on Cancer, Group 2a by the Environmental Protection Agency (EPA), and a 1B carcinogen by the European Chemical Agency.

Inside the body, cadmium causes cells to produce hydrogen peroxide, a substance that damages cells. This damage leads to the breakdown of important molecules like ascorbate and glutathione, which help protect cells. Hydrogen peroxide can also change protein structures by turning sulfur-containing groups into unusable forms and directly harm DNA in the cell’s nucleus. These harmful effects cause the cell to release large amounts of inflammatory signals.

Breathing in dust containing cadmium can quickly harm the lungs and kidneys, often leading to life-threatening kidney failure. Swallowing even small amounts of cadmium causes immediate poisoning and damage to the liver and kidneys. Substances that contain cadmium are also known to cause cancer.

Diagnosis

Increased levels of a substance called urinary beta-2 microglobulin in the body may signal early signs of kidney problems in people who have been exposed long-term to low but harmful amounts of environmental cadmium. Testing for urinary beta-2 microglobulin is a way to indirectly check for cadmium exposure. In certain situations, the Occupational Safety and Health Administration requires workers who have been exposed to high levels of cadmium over time to be tested for kidney damage. Blood or urine tests for cadmium are more effective for measuring exposure in industrial settings or after sudden poisoning. In cases of death caused by acute or chronic cadmium poisoning, measuring cadmium levels in organs such as the lungs, liver, or kidneys may be helpful. Healthy people who are not exposed to high levels of cadmium typically have less than 1 μg/L of cadmium in their blood or urine. The ACGIH biological exposure limits for cadmium are 5 μg/L in blood and 5 μg/g creatinine in urine for random samples. People with kidney damage from long-term cadmium exposure often have blood or urine cadmium levels between 25-50 μg/L or 25-75 μg/g creatinine. These levels are usually 1000-3000 μg/L and 100-400 μg/g creatinine in people who survived acute poisoning and may be much higher in cases of death caused by poisoning.

Treatment

A person with cadmium poisoning should receive immediate medical care to treat the condition and provide support.

For short-term exposure, vomiting inducers or stomach washing may help clean the stomach and intestines if done soon after exposure. Activated charcoal has not been proven effective. The US CDC does not recommend chelation therapy, partly because it may worsen kidney damage.

For long-term exposure, research shows that EDTA, a type of chelator, may help lower the body’s total cadmium levels. Giving antioxidants, such as glutathione, which helps protect the kidneys, may improve treatment results. For patients with very weak kidneys, limited research suggests that sauna sweating might help remove some cadmium, though this is not well-supported by evidence.

Epidemiology

In a large case of cadmium poisoning in Japan, older women who have gone through menopause are more likely to experience bone-related problems. The reason for this is not yet fully understood and is being studied. Cadmium poisoning in these women may increase the risk of developing osteoporosis, a condition that weakens bones. Research suggests that poor nutrition and difficulties with how the body uses calcium, which is common in older age, may be involved. Studies also indicate that damage to tiny structures in kidney cells called mitochondria, caused by cadmium, may play a key role in the disease.

History

In the early 1960s, an experiment was conducted where cadmium was sprayed over the city of Norwich. This information was made public in 2005 by the UK government, as reported by BBC News.

General and cited references

• Hartwig, Andrea (2013). "Cadmium and Cancer." Cadmium: Understanding Its Harmful and Beneficial Effects. A Series on Metal Ions in Life Sciences. Vol. 11. pp. 491–507. doi: 10.1007/978-94-007-5179-8_15. ISBN 978-94-007-5178-1. PMID 23430782.
• "Cadmium and You" (PDF). Bootle, UK: Health and Safety Executive. March 2010. Retrieved on January 29, 2011.
• Shannon M. "Heavy Metal Poisoning," in Haddad LM, Shannon M, Winchester JF (editors): Clinical Management of Poisoning and Drug Overdose (Third Edition, 1998).