Cadmium, a naturally occurring chemical element found in the earth's crust, is extensively used in a plethora of industries—from battery manufacturing to plastic stabilizing. Despite its extensive applications, cadmium can pose serious health hazards, particularly for workers involved in its extraction, refinement, and industrial use. In this article, we provide a comprehensive understanding of cadmium exposure and delve into ways to minimize risks and ensure a safer work environment.
What Is Cadmium?
Cadmium is a soft, bluish-white metal, chemically similar to zinc and mercury. Ranked 67th in abundance among the 82 naturally occurring elements, cadmium is relatively rare and found in minute quantities in air, water, soil, and food. Its widespread use in various industries means we all may have some level of exposure, although the degree varies significantly based on geographic location, occupation, and lifestyle.
Where Is Cadmium Found & How Is It Sourced?
Most cadmium used industrially is extracted during the production of other metals like zinc, lead, and copper. It is not typically mined on its own but rather obtained as a byproduct of the smelting and refining processes for these other metals. Industries that commonly use or produce cadmium include battery manufacturers, metal smelting companies, and producers of pigments, coatings, and plastics.
Cadmium can also be released into the environment through natural processes like volcanic eruptions, forest fires, and weathering of rocks. These sources can release cadmium into the air, where it then falls to the ground or into water bodies and gets absorbed by plants and animals, entering the food chain.
What Is Cadmium Used For?
Cadmium has diverse uses owing to its unique physical and chemical properties. It's primarily used in rechargeable nickel-cadmium batteries. Other applications include metal plating and coating, stabilizers in plastics, and as pigments in paints. It's also used in the manufacture of semiconductors and LCD panels.
Understanding Cadmium Exposure
People can be exposed to cadmium in several ways. The primary exposure source for the general population is diet, as cadmium is absorbed into plant and animal foods. Cadmium typically appears as a mineral combined with elements like oxygen, chlorine, or sulfur, and is present in almost all soils and rocks, including coal and mineral fertilizers. Additionally, smoking tobacco adds an extra burden of cadmium, as it is a key component in cigarette smoke, and its release into the environment often results from mining operations, wind and rain activity, forest fires, and volcanic eruptions.
However, for people working in industries where cadmium is used or generated, the exposure is significantly higher. Workers involved in mining, refining, or using cadmium-containing ores are at significant risk of exposure. Other high-risk professions include those involved in the manufacture of products containing cadmium, such as paints, and during work such as plating, soldering, and welding in cadmium-coated steel, cadmium smelting and refining, and cadmium alloy production.
Cadmium is widely used in the manufacture of batteries, particularly rechargeable nickel-cadmium batteries. Workers involved in the assembly of these batteries or in the recycling of old cadmium-containing batteries can face exposure to cadmium dust or fumes, particularly during processes such as welding or soldering. Adequate ventilation, substitution with less hazardous materials, and appropriate use of personal protective equipment are essential for reducing the risks associated with cadmium exposure in this industry.
Pigments & Metal Coating
Cadmium pigments, known for their brilliant hues and high durability, are used in various products, from plastics and ceramics to artists' paints.
Similarly, cadmium is used extensively in metal plating and coating for its corrosion-resistant properties particularly in harsh environments. Cadmium smelting, refining, and alloy production are essential processes in many industries, from aerospace to electronics.
Workers in these industries may be exposed to cadmium during the preparation, application, and finishing processes. Fume and dust extraction systems, along with stringent work practices, can significantly mitigate the risks associated with cadmium exposure.
Cadmium is used as a stabilizer in the plastics industry, particularly in the manufacturing of PVC. Workers in this sector can be exposed to cadmium during the mixing and molding processes. Substituting cadmium-based stabilizers with less toxic alternatives, providing appropriate ventilation, and enforcing rigorous personal hygiene practices are among the measures that can reduce cadmium exposure in this industry.
The Implications of Cadmium Exposure
Understanding cadmium toxicity is crucial, given its wide applications. Cadmium exposure, whether acute or chronic, can lead to adverse health effects. Acute inhalation of high levels of cadmium can result in flu-like symptoms and lung damage. In contrast, chronic exposure at low levels over an extended period can lead to kidney disease, bone disease, and even cancer.
Particularly at risk are workers who breathe in dust, fumes, or mists containing cadmium. Cadmium or cadmium compounds can also contaminate the skin, clothing, or food, leading to ingestion, another route of exposure.
Several reputable health and environmental bodies classify cadmium as a probable or known human carcinogen, including the EPA, IARC, ACGIH, and the NTP. This classification underscores the importance of adhering to safety standards and regulations when dealing with cadmium.
Recognizing the dangers of cadmium, the Occupational Safety and Health Administration (OSHA) and other agencies have set limits to protect people, particularly workers, from excessive cadmium exposure.
OSHA, for instance, has established the Permissible Exposure Limit-Time Weighted Average (PEL-TWA), or the permissible exposure limit over an 8-hour workday, for cadmium fumes to be 5 µg/m³. The National Institute for Occupational Safety and Health (NIOSH) sets an Immediately Dangerous to Life and Health level (IDLH) at 9 mg/m³.
Standards for Ensuring Worker Safety
Given the health risks associated with cadmium, regulations have been established across industries, including maritime, construction, and agriculture sectors, all aimed at protecting workers from exposure. They stipulate conditions for ensuring occupational safety and health in workplaces where cadmium is used or where workers could potentially be exposed.
Prevention: The Key to Managing Cadmium Exposure
Given the toxicity of cadmium and the lack of effective treatment for cadmium poisoning, prevention is the cornerstone of managing exposure. A crucial strategy is to eliminate or substitute cadmium wherever possible. Less toxic alternatives, such as nickel-metal hydride for rechargeable batteries or zinc and vapor-deposited aluminum for plating, can significantly reduce the risk of exposure.
Minimizing cadmium exposure begins with elimination or substitution at the top of the hierarchy, followed by engineering controls (like ventilation systems or isolating the source); administrative actions (limiting exposure time); work-practice controls; and finally, personal protective equipment (PPE) like proper respiratory protection and clothing.
The Path Forward: Ensuring Safety & Compliance
Occupational exposure to cadmium is a grave issue that demands stringent safety measures and constant vigilance. The key to managing exposure lies in preventive measures—from substitution of the substance to implementing rigorous control strategies. Understanding these risks and taking appropriate measures to mitigate them is not just important but crucial to ensuring the safety and health of all workers.