Chromium VI, also known as hexavalent chromium, is a form of chromium that has drawn public health attention. Its unique chemical properties and widespread environmental presence are a concern. Understanding its nature and potential impacts helps address associated risks.
Understanding Chromium VI
Chromium is a metallic element existing in several oxidation states. Trivalent chromium (Chromium III) and hexavalent chromium (Chromium VI) are the most common environmental forms. Chromium III is naturally occurring and an essential nutrient in trace amounts. In contrast, Chromium VI is largely a product of industrial processes and is highly toxic.
Chromium VI compounds are stable and soluble in water, allowing them to easily move through soil, water, and air. This mobility and solubility also enable Chromium VI to readily permeate biological membranes, including human skin. Most Chromium III compounds are sparingly soluble in water, making them less mobile.
Common Exposure Sources
Exposure to Chromium VI arises from industrial activities. Processes like electroplating, stainless steel production, and welding are major sources, as high temperatures convert other chromium forms into Chromium VI. Chromate compounds used in pigments (dyes, paints, inks, plastics) and as anticorrosive agents (paints, primers) also contribute to exposure.
Beyond industrial settings, environmental contamination can lead to exposure. Chromium VI enters groundwater from weathering rocks or industrial waste disposal. Contaminated drinking water sources have been a concern. Some consumer products, including certain inks, paints, paper, and treated timber, may also contain Chromium VI.
Health Implications
Exposure to Chromium VI can lead to adverse health effects, varying by route and duration. Inhalation of airborne Chromium VI is a known human carcinogen, increasing lung cancer risk. Studies show elevated lung cancer rates in workers exposed to high levels. The latency period can be up to 20 years.
Inhaling Chromium VI can cause acute irritation to the nose, throat, and lungs, with symptoms like runny nose, sneezing, coughing, and a burning sensation. Chronic inhalation may lead to severe respiratory issues, including nasal septum ulceration and perforation, bronchitis, decreased lung function, and occupational asthma.
Ingesting large amounts of Chromium VI can cause gastrointestinal effects like abdominal pain, vomiting, and diarrhea, and may lead to kidney and liver damage. Direct skin contact with Chromium VI solutions or dusts can cause skin irritation, allergic contact dermatitis, and deeply penetrating skin ulcers, sometimes called “chrome holes.”
Reducing Exposure and Risk
Minimizing Chromium VI exposure involves safety measures and general awareness. In occupational settings, proper ventilation systems control airborne concentrations. Workers should use personal protective equipment (PPE), such as respirators, gloves, and protective clothing, to prevent inhalation and skin contact. Regular medical surveillance, including skin and respiratory tract examinations, is also part of occupational safety programs.
Regulatory bodies like OSHA set permissible exposure limits (PELs) for airborne Chromium VI. The EPA also sets maximum contaminant levels for total chromium in drinking water. For the general public, awareness of water quality and avoiding unnecessary contact with dust and soil that may contain Chromium VI are practical steps.