Chromium is a naturally occurring metallic element found in the Earth’s crust, soil, water, plants, and animals. While some forms of chromium are beneficial and even necessary for the body’s proper functioning, others can be harmful. Chromium toxicity refers to any detrimental effect on an organism or cell resulting from exposure to specific, poisonous forms of chromium.
Forms of Chromium and Their Toxicity
Chromium exists in various oxidation states, but the two most common and biologically significant forms are trivalent chromium (Cr(III)) and hexavalent chromium (Cr(VI)). Trivalent chromium is considered an essential trace element for human nutrition, playing a role in regulating sugar and fat metabolism. It generally exhibits low toxicity due to its poor absorption through the gastrointestinal tract and limited ability to cross cell membranes.
In contrast, hexavalent chromium is highly toxic and is primarily associated with industrial processes rather than natural occurrence. Cr(VI) is readily absorbed by the body through various routes, including inhalation, ingestion, and skin contact, and can efficiently enter cells. Once inside the body, Cr(VI) is known to be genotoxic, meaning it can damage genetic information in living cells, potentially leading to DNA mutations and cancerous tumors. The toxicity of hexavalent chromium is significantly greater than that of trivalent chromium.
Sources of Harmful Chromium Exposure
Exposure to harmful forms of chromium primarily occurs in industrial settings. Common sources include electroplating, welding of stainless steel and other alloys, and the production of chromate pigments, dyes, and paints. Other industrial applications contributing to exposure involve leather tanning, textile manufacturing, and wood preservation. Workers can inhale dusts, mists, or fumes containing Cr(VI) during these processes.
Environmental contamination also serves as a source of exposure, with industrial waste sites and contaminated water supplies being significant concerns. People living near facilities that manufacture or process chromium, or near waste disposal sites, may experience elevated exposure levels. Less commonly, over-supplementation with certain chromium forms can also lead to toxicity. Ingestion can occur if workers consume food or drink with contaminated hands, or if contaminated water is consumed.
Signs and Symptoms of Chromium Toxicity
The signs and symptoms of chromium toxicity vary depending on the form of chromium, the route of exposure, and the duration and concentration of exposure. Inhalation of hexavalent chromium can lead to significant respiratory issues. Symptoms include irritation of the nose, throat, and lungs, characterized by runny nose, sneezing, coughing, and wheezing. Prolonged or repeated exposure can cause nasal sores, ulcers, and even perforation of the nasal septum. Occupational asthma and lung cancer are also well-documented risks associated with chronic inhalation exposure.
Skin contact with hexavalent chromium can result in dermatitis and the formation of skin ulcers, sometimes called “chrome ulcers.” These ulcers are typically small, crusted sores with a rounded border that heal slowly and may leave scars. Some individuals may develop allergic contact dermatitis, causing swelling, a red, itchy rash, and skin thickening that can worsen with repeated contact. Eye irritation and damage can also occur from direct contact.
Ingestion of hexavalent chromium can cause gastrointestinal issues such as abdominal pain, vomiting, and hemorrhage. Other effects may include mucosal burns, an inflamed stomach lining, and ulcers. Systemic effects can involve damage to organs, including kidney and liver dysfunction, which may manifest as sudden kidney failure or jaundice. In severe cases of high-dose exposure, breakdown of muscle tissue and damage to the immune and reproductive systems have been reported.
Managing and Preventing Chromium Toxicity
Managing suspected chromium toxicity begins with immediate removal of the individual from the source of exposure. For respiratory symptoms, supportive care such as humidified oxygen, ventilatory support, bronchodilators, and expectorants may be administered. If chromium has been ingested, induction of vomiting is generally not recommended due to the potential corrosive effects of chromium compounds. Gastric lavage with an antacid like magnesium hydroxide might be considered, and oral ascorbate has shown protective effects.
Diagnosis often involves a medical history and physical examination, along with specific tests like blood or urine chromium levels. However, interpreting these levels, especially for hexavalent chromium, can be challenging. While no specific antidote exists for chromium poisoning, treatments like hemodialysis, ascorbic acid, N-acetylcysteine, and calcium disodium edetate (EDTA) may be used to help eliminate chromium from the body in severe cases.
Prevention of chromium toxicity centers on minimizing exposure, particularly in occupational settings. This involves proper ventilation in workplaces, using personal protective equipment to prevent inhalation and skin contact, and safe disposal of industrial waste. For the general public, avoiding known contaminated areas and exercising caution with dietary supplements containing chromium. Patients with occupational exposure should be informed about potential long-term effects and monitoring options for early detection of complications.