Environmental Health: Health Effects of chromium Ⅵ and Its Compounds

Environmental Health: Health Effects of chromium Ⅵ and Its Compounds

■  Chromium Ⅵ is a substance recognized by the International Agency for Research on Cancer (IARC) as carcinogenic to

    humans. It's classified as Group 1.

■   Globally Harmonized System of Classification & Labeling of Chemicals

 

<Globally Harmonized System of Classification & Labeling of Chemicals>

 

■    Properties

Chromium is a gray-white metal that exists in the natural environment and in the bodies of plants and animals.

Chromium is used in the manufacture of various alloy products such as stainless steel, and welding rods used during welding work also contain chromium.

Naturally existing chromium Ⅲ exists in the human body as is and is not carcinogenic, while artificially produced chromium Ⅵ does not change in its natural state and is carcinogenic.

 

■   Environmental exposure in the general population

Chromium is mainly exposed through the respiratory tract and digestive system, and the general public is mainly exposed to chromium through smoking.

 

■   Occupational exposure

Workers in various industries, including non-ferrous metal smelting, alloying, chrome plating, and pigment manufacturing, may encounter chromium Ⅵ exposure.

Chromium is used in making different alloy products like stainless steel, and some welding rods contain chromium. When these alloys are manufactured or welded, metal fumes containing chromium Ⅵ are produced. Chrome plating, which uses chromium for its excellent wear resistance and shine, also exposes workers to chromium Ⅵ.

Additionally, chromium is used in dye manufacturing, so workers in paint and textile dyeing operations may also be exposed to chromium Ⅵ. Other industries like leather processing, wood preservation, glass manufacturing, and catalyst production are also sources of occupational exposure to chromium Ⅵ.

Even cement contains chromium Ⅵ, so workers involved in cement manufacturing, transportation, and construction may face exposure to chromium Ⅵ through cement dust.

 

■   Biological properties and mechanisms

The absorption rate of chromium varies depending on the solubility of the chemical (water), dietary form, and anion (salt). The absorption of chromium after oral administration is relatively low, and absorption rates of 2% for trivalent chromium and 7% for chromium Ⅵ are generally reported. The absorption rate of both trivalent and chromium Ⅵ increases in the gastrointestinal tract when fasting. Pulmonary absorption of inhaled chromium is estimated to be greater than absorption through the stomach, and 20-30% of the exposure amount for highly water-soluble chromium Ⅵ enters the bloodstream.

Chromium Ⅵ can penetrate the plasma membrane of cells, so its level in the body is higher than that of trivalent chromium, and it can also penetrate the placenta, so it can be transmitted to the fetus.

Chromium Ⅵ is reduced by ascorbate, glutathione, and cysteine, and if there is enough reducing agent, it is ultimately reduced to trivalent chromium in most cases. If the concentration of the reducing agent in the cell is insufficient, the chromium intermediate, or pentavalent, is present and active oxygen is generated, causing oxidative stress in the cell and damaging DNA.

 

■   Environmental health effects

 

<Acute Effects>

Inhaling high concentrations of chromium Ⅵ can irritate the nose and throat, leading to symptoms like a runny nose, sneezing, coughing, itching, and burning sensation. Skin contact can cause irritant contact dermatitis or allergic contact dermatitis, while contact with the eyes may result in irritation and damage.

 

<Chronic Effects>

 

1.     Cancer

Chromium Ⅵ is classified by the International Agency for Research on Cancer (IARC) as a definite carcinogen, particularly linked to lung cancer in humans. Long-term exposure to chromium Ⅵ compounds heightens the risk of developing lung cancer. There's some evidence suggesting an increased risk of nasal and paranasal sinus cancers, although this evidence is limited.

 

2.     Respiratory System

While inhaling small amounts of chromium Ⅵ typically doesn't cause respiratory irritation, some individuals may experience asthma symptoms like wheezing and shortness of breath due to allergic reactions. Chronic exposure to chromium fumes can lead to conditions such as chronic bronchitis, interstitial pneumonia, and severe pulmonary fibrosis. Repeated or prolonged exposure may also result in nasal inflammation, nosebleeds, and potentially the formation of a hole in the nasal septum.

 

3.     Skin

Handling liquids or solids containing chromium Ⅵ can trigger allergic contact dermatitis, characterized by swelling, a red, itchy rash, and eventual hardening and thickening of the affected area with prolonged exposure. Additionally, chromium Ⅵ can cause non-allergic skin irritation, potentially leading to chromium ulcers when in contact with damaged skin.

 

■    References

Casarett & Doull’s Toxicology : The Basic Science Of Poisons, 2019.

ATSDR. Toxicological Profile for Chromium. Atlanta, GA: Agency for Toxic Substances and Disease Registry; 2012b. Available at: http://www.atsdr.cdc.gov/toxprofiles/tp.asp?id=62&tid=17.

IARC. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. Arsenic, Metals, Fibres, Dusts: Nickel and Nickel Compounds. Lyon, France: International Agency for Research on Cancer; 2017.

Available at: http://monographs.iarc.fr/ENG/Monographs/vol100C/mono100C-10.pdf.

HBM4EU. Suggested list of biomarkers, matrices and analytical methods for the 1st prioritisation round of substances.

Available at: https://www.hbm4eu.eu/wp-content/uploads/2018/09/Deliverable-9.2-Prioritised-list-of-biomarkers-matrices-and-analytical-methods-for-the-1st-prioritisation-round-of-substances.pdf

NTP. 15th Report of Carcinogens. 2021. Available at: 15th Report on Carcinogens (nih.gov)