The RoHS Directive adopts an extremely strict approach towards cadmium, characterized by a "principle of total prohibition, with conditional exemptions only in very few specific cases where substitution is currently impossible." The restriction on cadmium is the most stringent among all regulated substances, with a limit of 0.01% (100 ppm by weight in homogeneous material). This means that in any single homogeneous material within an EEE product, the cadmium content must not exceed 0.01% of its weight. In contrast, the limit for other restricted substances (such as lead, mercury, hexavalent chromium, etc.) is 0.1% (1000 ppm), underscoring the heightened concern regarding its hazards.

Primary Reasons for the Strict Restriction on Cadmium:

•High Toxicity: Poses serious risks to human kidneys, bones, and the respiratory system; it is a recognized carcinogen.

•Bioaccumulation: Once released into the environment, it accumulates in organisms and soil, and is difficult to degrade.

•Environmental Pollution: Improper disposal of waste electronic products can lead to cadmium leaching into soil and groundwater, causing long-term contamination.

•Plastic Stabilizer: Cadmium stearate was used as a heat stabilizer in older plastics like PVC.

•Electroplating: Used for anti-corrosion coatings on steel parts or as an undercoat for other platings.

•Batteries: Nickel-Cadmium (Ni-Cd) batteries are the most well-known application. While largely replaced by lithium-ion batteries in consumer electronics, they are still used in specific industrial applications.

•Pigments: Cadmium-based pigments (cadmium yellow, cadmium red), known for their bright and stable colors, were used in plastics and certain ceramic glazes.

•Low-Melting-Point Solder: Some special alloy solders may have contained cadmium.

•Electronic Components: Older photoelectronic semiconductors, switches, and contacts may contain cadmium.

Current Exemptions (Temporary and Limited):The RoHS Directive acknowledges that technically feasible alternatives for cadmium may not exist in certain specific cases. Therefore, it maintains a list of exemptions which are granted under specific conditions, have expiration dates, and are subject to periodic review to encourage eventual substitution.

As of the latest directive (RoHS 3, Directive 2011/65/EU and its amendments), selected limited and time-bound exemptions related to cadmium include:

•Exemption 7(c)-I: Cadmium and its compounds in electrical contacts.

•Exemption 7a: Cadmium used as a corrosion inhibitor in the carbon steel cooling system of absorption refrigerators, not exceeding 0.2%.

•Exemption 41: Cadmium contained in quantum dots used in colour-converting II-VI LEDs (< 0.2 µg Cd per mm² of light-emitting area) for solid-state lighting or displays.

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