Science & Research
Volume IV - 6.1 Introduction
Orientation and Training
|VERSION NO.: 1.4|
Section 6 - Elemental Analysis
|EFFECTIVE DATE: 10-01-03||REVISED: 02-14-13|
- 6.1.1 FDA Center for Food Safety
- 6.1.2 Lead and Cadmium in Foods and Foodware
- 188.8.131.52 Lead and Cadmium in Foods
- 184.108.40.206 Lead and Cadmium in Housewares
- 6.1.3 Mercury in Food
- 6.1.4 Other Elements in Food
Man and other animals are exposed daily to numerous elements, in varying forms and levels, through food (feed), water, and other FDA-regulated products.
Major essential elements include C, H, O, N, S, Ca, P, K, Na, Cl, and Mg. C, H, O, N, and S make up the bulk of the elemental constituents of plants and animals, and are the major components of the organic substances in tissues.
Fe, Zn, Cu, Co Mn, I, Mo, Cr, Se, F, (B for plants) have identified functions meeting the definition of essential elements in animals including man (References 1, 2). Whether an element is essential has little, but some bearing on an element's toxicity. Essential elements under homeostasis, (i.e. the level of absorption, body stores, and or excretion is under physiological control), tend to have a lower relative toxicity. However, many factors, such as the level of exposure, the form of the element, the sensitivity of the host, the physiological and nutritional status of the host, affect the toxicity of an element.
Nonessential and essential elements can be toxic. Nonessential elements where human toxicity has been reported includes Pb, Cd, Hg, As, Al, Ba, Li, Pt, Te, Ti, Sb, Be, Ga, In, V, Ni, Sr, Sn, Ge, Ag, Au, Bi, Tl, and U. The essential elements, F, Co, Fe, Mo, Cu, Mg, Se, Cr, Mn, and Zn, are of practical toxicological significance. Se is the most toxic essential mineral elements. Presently, Pb, Cd, Hg (as methylmercury), and As (inorganic forms) are of the greatest concern and have the greatest program emphasis.
This training chapter will provide the following information:
- Sources of Contamination,
- Compliance Policy Guide References,
- lead and cadmium in food and foodware,
- methylmercury in food, and
- Instruction for the analytical exercises.
As part of its responsibilities for ensuring food safety, the FDA Center for Food Safety and Applied Nutrition (CFSAN) routinely monitors the level and potential dietary uptake of these toxic elements (contaminants) in foods and foodware. FDA Compliance Program Guides detail the sample collection and analysis for the determination of lead and cadmium in foods and foodware, and methyl mercury, arsenic and selenium in food.
The Total Diet Study (TDS), sometimes called the Market Basket Study, is an ongoing FDA program that determines levels of various pesticides, contaminants, and nutrients in foods for the purpose of estimated intakes of these substances in representing diets of selected age-sex groups in the United States Population. Elements analyzed include the following: arsenic, cadmium, calcium, copper, iron, lead, magnesium, manganese, mercury, nickel, phosphorous, potassium, selenium, sodium, and zinc (Reference 22).
Presently, the compliance programs cover toxic elements in food (CPG 7304.019A), and housewares (CPG 7304.019B). See Reference 3.
Lead in the diet can be attributed to natural sources of lead in the soil, deposition of lead particles onto crops, pollution (lead gasoline usage), food processing and packaging techniques, herbal supplements and folk remedies. The use of lead-based solders in food cans is now prohibited (21CFR 189.240). Although the use of lead based pigments in food wrappers is not prohibited, the United States and European Commission voluntarily stopped this practice. Candy food wrappers from other countries, particularly Mexico, have been found to contain percent levels of lead. Lead is found in folk remedies such as Azarcon, Greta, herbal medicines, and unapproved dyes in eye cosmetics (kajal, surma, kohl) from the Far and Middle Eastern countries (Reference 19).
Cadmium is found in foods naturally and due to pollution. Cadmium is emitted into the atmosphere from smelters and waste incineration plants; the use of municipal sludge can dramatically increase cadmium levels in food. Recently cultivated agricultural areas derived from ancient seabeds are prone to producing elevated levels of cadmium in foods (e.g. spinach, lettuce). See Reference 17.
Pigments used to decorate ceramicware, or glazes coating ceramicware may contain lead or cadmium. Traditional wares (e.g. Chinese classic enamel-on-porcelain wares, Mexican glazed folk terra cotta) have been found to contain excessive amounts of lead (Reference 3). Glazes that are improperly formulated, applied, or fired may permit unacceptable amounts of lead or cadmium to leach into food. The following colors in glaze or decorations are often indicative of ceramicware that may release cadmium: red, orange, yellow.
See Compliance Program Guidance Manual 7304.019A, Toxic Elements in Foods. Lead and cadmium are identified as the toxic elements of concern in foods; particular emphasis is placed on foods consumed by children who are the most sensitive to adverse side effects.
There are no regulatory limits, i.e. tolerances, for toxic elements in foods; sample results that exceed normal concentrations are brought to the attention of CFSAN, who will conduct an assessment of potential health hazards from the quantity of the toxic element found based upon food consumption of the product.
FDA has established Provisional Daily Total Tolerable Intakes (PDTTI) for lead for several at-risk groups (Reference 7). When the consumption of a contaminated food has exceeded a PDTTI, regulatory action may be taken on an ad hoc basis. Food Chemical CODEX (FCC) lists many internationally recognized standards for lead in foods and food ingredients. While these are not regulatory tolerances, the FFC are often employed as lowest limits of actions for imported foods.
The prohibition of lead soldered cans and the removal of lead from gasoline have significantly reduced the lead exposure to the average consumer. The Total Diet Surveys indicate the average lead intake from food has decreased more than 95% since the 1970s. Nonetheless, FDA remains concerned about lead in regulated products, especially since more than half of our foods now come from outside the U.S., and a significant number of children in the U.S. remain exposed to excessive amounts of lead.
See Compliance Program Guidance Manual 7303.019B.
The Food Additives provision of the FD&C Act does not permit a harmful level of a substance to migrate from the surface onto a food or beverage. Toxic Elements in Houswares (CPGM 7303.019B) focuses on lead and cadmium found in ceramicware and silver plated hollowware used for eating, storing, holding and cooking foods.
The FDA and the State Administration of Entry/Exit Inspection and Quarantine of China (recently renamed the China National Certification and Accreditation Administration or CNCA) implemented an Memorandum of Understanding (MOU) pertaining to the safety of ceramic table ware produced in China and exported to the United States. The MOU specifies a certification system for ceramic tableware production facilities in China. This certification system is expected to provide FDA with reasonable assurance that ceramicware produced in these facilities and exported to the United States will not exceed FDA action levels for leachable lead and cadmium (Reference 20).
The CPGM focuses on the following areas: investigates the rate of compliance for Chinese Ceramicware from non-certified and certified factories, audits the effectiveness of the China certification program in improving the safety of ceramicware exported to the United States, and concentrates on sampling countries with prior violations, particularly small shipments entering from Mexico.
Monitoring of ceramicware is conducted in two steps. Screening tests for ceramicware are conducted in the field to identify items that are likely to contain leachable lead. Based on the results of the screening tests, official samples are collected and sent to the laboratory for further testing. There is no screening test for cadmium in ceramicware, or lead and cadmium in silver-plated hollowware. The investigator is directed to look for signs of improper glazing on the product, and/or collecting samples with those colors that may contain lead or cadmium.
In the absence of codified regulations or tolerances for ceramicware, FDA has established interim action guidelines for lead (CPG Sec 545.450) and cadmium (CPG Sec 545.400). See References 4 and 5. The surveillance of leachable lead and cadmium in ceramicware continues to be a program priority.
Past FDA regulatory efforts, an MOU with China, efforts by the commercial sector, and state regulations (e.g. California Proposition-65), have led to a vast improvement in the performance of daily-use tableware regarding the leachability of lead and cadmium. Most daily-use ceramicware pose relatively few regulatory problems for leachable levels of lead and cadmium. The traditional wares (especially from China) and folk terra cotta wares from Mexico and Central American countries continue to pose an extreme lead exposure risk, especially for children and the fetus. Many other elements are used in ceramicware bodies, their glazes, and decorations. Ba, Sb, Co, Cr, and others may leach from ceramicware. However, the regulatory significance of these elements has not been evaluated.
See Compliance Policy Guide, Section 540.600, Fish, Shellfish, Crustaceans and other Aquatic Animals – Methyl Mercury (Reference 9).
Mercury, primarily as methyl mercury, was first identified as a regulatory issue in seafood in the 1970s. Mercury occurs naturally in the environment, and is released from the Earth's crusts and oceans. Mercury is also released from fossil fuels such as coal, and burning industrial wastes. Fish absorb methyl mercury from water as it passes over their gills and through feeding aquatic organisms; methyl mercury binds tightly to proteins in fish tissue (Reference 21).
Studies where people were exposed to high levels occurred in highly contaminated fish in Minnamata, Japan. Over one hundred people died from eating fish (often daily over extended periods) from waters that were severely polluted with mercury from industrial discharge. Mercury poisoning occurred in unborn fetuses and children. An epidemic of mercury poisoning occurred with a wheat seed treated with alkyl mercury fungicide (Reference 21).
Presently, the FDA regulatory guideline for methyl mercury in seafood (CPG Sec 540.600) is one part per million (ppm) methyl-mercury expressed as Hg. FDA's action level of one ppm for methyl mercury in fish was established to limit the consumers methyl mercury exposure to levels ten times lower than the lowest levels associated with adverse effects.
Arsenic and Selenium occur naturally in foods. Both can be present at toxicologically significant levels in groundwater and in soils.
Arsenic compounds are released to the atmosphere from natural and industrial sources. The major sources of arsenic emissions are the smelting of metals, burning of fossil fuels, and application of pesticides and herbicides. The arsenic compounds may accumulate in agricultural and horticultural soils and plants.
Arsenic in food is most often in alkylated forms. The alkylated forms of arsenic that arise in plants, shrimp (Reference 16), and some other animals have a relative low order of toxicity. Arsenate and arsenite are far more toxic and have proven to be carcinogenic in humans.
Selenium is the most toxic essential mineral element. Selenium often occurs as selenium analogues of sulfur-containing amino acids and metabolites in plants. While there have been numerous selenium intoxications reported for man and other animals, these poisonings have been mainly due to errors in manufacturing dietary supplements and feed selenium supplements. Although human toxicity to selenium has been reported in China and other parts of the world where extreme selenium pollution exists, selenium deficiency appears to be the more significant public health concern.