Cadmium Exposure and Testing
By Elisabeth Lutanie, Ph.D.
Cadmium is a transitional metal that can have harmful cumulative effects on the human body. This article explains what cadmium is, where it comes from, how people get exposed to it, and how laboratories can test for it.
What is Cadmium?
Cadmium (Cd, atomic number 48) is a silver- or bluish-white metal in the group 12 of the periodic table. It is usually found with an oxidation state of +2 and combined with other elements such as oxygen (cadmium oxide), chlorine (cadmium chloride), or sulfur (cadmium sulfate, cadmium sulfide). It is also a cumulative poison associated with an array of syndromes such as renal dysfunction, reproductive toxicity, and bone defects. It is classified as a human carcinogen (Group 1) by the International Agency for Research on Cancer , and as a probable human carcinogen (Group B1) by the Environmental Protection Agency (EPA).
Although its absorption in humans is relatively low, cadmium can accumulate in the body and become a major concern over time when individuals are chronically exposed to cadmium. The exact half-life of cadmium in the body is not known, but it is thought to be as long as 30 years . This long half-life results mainly from the fact that humans do not have an effective cadmium elimination pathway.
Where Does Cadmium Come From?
Cadmium is released to the atmosphere both from natural sources and from human activities. Industrial activities such as combustion of fossil fuel, incineration of municipal or industrial wastes, and phosphate fertilizer manufacturing are the main sources of atmospheric cadmium. Cadmium air levels are usually thousands of times greater in the workplace of people involved in mining or manufacturing industries than in the general environment; people can be exposed to atmospheric cadmium from the smelting and refining of metals or from the air in plants that make cadmium products such as batteries (e.g. nickel-cadmium), coatings, pigments, or plastics.
Cadmium occurs naturally in zinc, lead, copper, and other ores which can serve as sources to ground and surface waters, especially when in contact with soft, acidic waters. However, groundwater rarely contains high levels of cadmium unless it is contaminated by mining, discharges from industrial facilities or sewage treatment plants, or seepage from hazardous waste sites. Cadmium can also be released into drinking water by corrosion of some galvanized plumbing and water pipes.
Cadmium concentrations in drinking water supplies are typically less than 1 µg/L (1 ppb). The Environmental Protection Agency (EPA) and some states regulate the amount of cadmium discharged in industrial wastewaters, and the EPA has established a maximum contaminant level (MCL) for cadmium in drinking water of 5 µg/L (5 ppb), suggesting that drinking water containing cadmium levels less or equal to the MCL are safe. The MCL value is also the lowest level to which water systems can reasonably be required to remove cadmium from the water, given the present technology and resources .
How are People Exposed to Cadmium?
The main exposure to cadmium, in people, occurs through the consumption of foods and drinking water, the inhalation of cadmium particles from ambient air or cigarette smoke, and the incidental ingestion of contaminated dust or soil. Foods (e.g. grains, cereals, leafy vegetables) that have been contaminated through water and crops grown on polluted soil are the highest source of cadmium exposure for the general population . People with low calcium, protein, or iron reserves appear to absorb cadmium more efficiently and may be at increased risk of developing toxicity.
Cigarettes are also a significant source of cadmium exposure. Tobacco leaves accumulate large amounts of cadmium and it has been estimated that tobacco smokers (at one pack per day) typically have cadmium blood and body burdens at least twice as high as non-smokers . Each cigarette contains 1 to 3 μg of cadmium and approximately 10% is inhaled into a smoker’s lungs during active smoking. 
Lately it’s been reported that people are being exposed to cadmium from some jewelry. According to a study by the Associated Press (AP) cadmium emerged as a safety concern after AP’s investigation revealed that lab tests conducted on 103 pieces of low-priced children’s jewelry found 12 items with cadmium content above 10 percent of the total weight. 
How Do Laboratories Test for Cadmium?
Quantitative determination of cadmium can be performed using a variety of methods and techniques, including:
- Atomic absorption spectroscopy (AAS) with either a graphite furnace (GFAA, EPA Method 213.2) or flame (FAA, EPA Method 231.1)
- Inductively coupled plasma techniques (ICP) using optical emission spectroscopy (ICP-OES) or atomic emission spectroscopy (ICP-AES, EPA method 200.7)
- Mass spectrometry (ICP-MS, EPA method 200.8)
- Electrochemical techniques such as adsorptive cathodic stripping voltametry (ACSV) [8, 9], potentiometric stripping analysis (PSA) , and liquid chromatography  are also used to analyze and separate cadmium (Cd (II))
Laboratories such as Columbia Analytical Services offer a range of analytical testing methods for cadmium, including ICP-AES and ICP-MS. The choice of the detection procedure is based on various parameters, including quality data requirements and sample media.
ICP/AES and ICP/MS are the most commonly used instruments for testing both biological materials and environmental samples, although GFAAS is still appropriate for certain applications. ICP-MS offers the best sensitivity and generally provides excellent selectivity. For aqueous samples, a typical reporting limit is 0.02 ug/L, 1/25th of the MCL. Analysis by ICP/AES with axial viewing is simpler, but also less sensitive (i.e., the typical reporting limit is approximately 0.5 ug/L). Reporting limits for solid samples are in the general range of 0.05 mg/kg by ICP/MS and 0.1 mg/kg for ICP/OES.
Environmental samples analyzed by ICP/AES or ICP/MS usually undergo an acid digestion procedure, a pre-concentration treatment via chemical separation, or a direct aspiration (with no preparation). The three most common methods used for cadmium sample digestion are:
1) Dry-ashing in a conventional oven followed by acid dissolution of the residue
2) Oxidative acid digestion by heating in a pressure vessel
3) Oxidative acid digestion at atmospheric pressure
Much progress has been made in the development of easy-to-use on-site tests for fast detection of trace levels of cadmium in food and environmental samples. Various commercial kits are available that allow individuals to screen quickly for cadmium on solid surfaces or in liquids, although the kits have a higher detection limit than the more sophisticated laboratory procedures.
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Tags: cadmium, cadmium chloride, cadmium oxide, cadmium sulfate, cadmium sulfide, cancer, carcinogen, EPA, fossil fuel, General Lab Testing, ICP-AES, ICP-MS, ICP/AES, ICP/MS, Laboratory, Metals, testing