Why does Cadmium appear in food, and how harmful is it?

Long-term cadmium poisoning will damage kidney function, increase the excretion of low molecular weight proteins in urine, and create kidney stones.

Why is cadmium in food?

A bar of 99% pure cadmium - (Photo: WIKIMEDIA).

A lecturer in the chemistry department at the University of Natural Sciences (Vietnam National University, Ho Chi Minh City) said that cadmium is a heavy metal with a bluish white color.

Normally cadmium is rarely detected in pure form but is often combined with a number of elements to form compounds such as cadmium oxide, cadmium sulfide, cadmium chloride, cadmium sulfate.

In nature, cadmium compounds are often present with some phosphorus compounds. This is the reason cadmium often appears in some types of fertilizers, especially phosphorus fertilizers.

Researchers from the ICAR Institute (India) believe that an important raw material for producing phosphorus-containing fertilizers is phosphate rock . These rocks often contain cadmium compounds. 

During the process of deposition over millions of years, cadmium originates from volcanic rocks along with phosphorus from animal bones, condensing into phosphate minerals.

Some types of phosphorus fertilizers often contain high amounts of cadmium - (Photo: ALAMY).

While phosphorus is an important element that promotes the growth and development of plants, supporting roots, flowers, and fruits, cadmium does not have any significant effect on plant growth but also affects the health of plants. Human health if large amounts of cadmium are consumed through food.

However, in the fertilizer production process, many factories have difficulty or are not "interested" in completely eliminating the amount of cadmium contained in natural materials, partly due to the cost, partly because it will affect to the quality of fertilizer.

Excess cadmium in fertilizers can build up over time, enter the soil and then accumulate in plants.

According to chemical experts at Zhongshan University, Guangzhou (China), cadmium residue in agricultural products is also caused by cadmium pollution in the soil. 

In some areas, mining and metallurgical activities emit smoke or dirty water containing cadmium, thereby exposing land. Substandard soil improvement and irrigation management methods will not control cadmium pollution.

Cadmium harms kidneys, bones, and breathing

According to the World Health Organization (WHO), food is the largest source of cadmium accumulation in the body other than smoking. What is worrying is that cadmium can travel "a long way", from minerals, soil, plants and then into the human body.

Some foods such as green vegetables, peanuts, soybeans, sunflower seeds, potatoes and other grains, starches. can contain high levels of cadmium if grown on heavily cadmium-contaminated soil or used fertilizer. Fertilizers contain large amounts of cadmium. Some surveys show that 98% of the average amount of cadmium a person can consume comes from terrestrial foods, 1% from seafood, and 1% from drinking water.

Also according to WHO, the allowable safe limit of cadmium in drinking water is 3µ/l, in air is 5ng/m3, the temporary acceptable weekly intake is 25µg/kg. Exceeding this threshold, cadmium accumulation over time will leave long-term harmful effects.

Some types of seafood have high levels of cadmium - (Photo: NEW FOOD MAGAZINE).

According to Nha Trang Pasteur Institute, cadmium accumulates mainly in the kidneys over a relatively long period of time from 10-35 years . Eating foods containing high amounts of cadmium will cause digestive disorders such as nausea, vomiting, abdominal pain, and diarrhea.

Long-term poisoning will damage kidney function , increase the excretion of low molecular weight proteins in urine, and create kidney stones.

Cadmium poisoning also causes calcium metabolism disorders , leading to bone diseases such as bone weakening, bone deformation, bone tissue destruction, causing osteoporosis and bone pain.

In addition, cadmium also causes damage to the respiratory tract with symptoms such as rhinitis, decreased sense of smell, and loss of smell. Inhaling dust containing cadmium oxide in high doses causes acute pneumonia that can lead to death.

Long-term occupational exposure to high levels of cadmium causes symptoms of bronchitis and chronic pneumonia (cough, difficulty breathing, chest pain, fever); contributes to the development of lung cancer.