There is nothing good about Cadmium in the human body. Here we report many ways adults and children can be exposed to cadmium and the unusual resultant health effects.
Last updated: August 2018
Image source: https://en.wikipedia.org/wiki/Cadmiumction_trend.svg
The half-life of cadmium is 10 to 30 years in humans. Cadmium slowly accumulates in organs, such as the kidneys and bone, and causes chronic damage, such as renal dysfunction and fractures. Long-term exposure to low-dose cadmium has been associated with increased oxidative stress and kidney tubular impairment and body cadmium levels are correlatde with diabetes and high blood pressure. In 1993, IARC classified cadmium and its compounds as human carcinogens and recent studies have shown that dietary cadmium exposure is associated with the development of postmenopausal breast cancer.
Ref: Exposure assessment of dietary cadmium: findings from shanghainese over 40 years, China
Cover image Photo: Tiraya Adam on Unsplash
Food Sources of CADMIUM
The Clean Label Project tests for Cadmium in foods sold in the US. They test baby food, pet food and much more. Unfortunately they found detectable levels of cadmium in baby foods and protein powders.
For context: “To prevent health risk from cadmium contamination, a provisional tolerable weekly intake (PTWI) for cadmium of 7 μg/kg body weight was established by the Joint FAO/WHO Expert Committee on Food Additives in 2004. In 2010, the 73rd JECFA reevaluated cadmium intake levels based on findings from a number of recent epidemiological studies and established a provisional tolerable monthly intake (PTMI) of 25 μg/kg body weight based on the long half-life of cadmium.” Ref: Exposure assessment of dietary cadmium: findings from shanghainese over 40 years, China
See the Clean Label Project for details.
For the US population, the geometric mean daily intake of cadmium in food is estimated to be 18.9 μg/day. In most countries, the average daily intake of cadmium in food is in the range of 0.1–0.4 μg/kg body weight.
In diets with low iron, calcium, or protein, it is possible that more cadmium is absorbed.
Because tobacco leaves naturally accumulate large amounts of cadmium, cigarettes are a significant source of cadmium exposure for the smoking general population. It has been estimated that tobacco smokers are exposed to 1.7 μg cadmium per cigarette, and about 10% is inhaled when smoked. Note that when smoking, part of the Cadmium is swallowed and absorbed through the gut.
“Low levels of cadmium have been measured in most foodstuffs (average concentrations are less than 0.02 µg/g). Factors influencing cadmium levels in food include: food type (e.g. seafood or leafy vegetables versus meat or dairy), growing conditions (e.g. soil type, water), agricultural and cultivation practices, meteorological conditions (i.e. rate of atmospheric deposition), and anthropogenic contamination of soil or aquatic system . The use of cadmium-containing fertilizers in agriculture increase cadmium concentrations in the crops, and derived products.
High concentrations of cadmium are found in leafy vegetables (e.g. lettuce, spinach), starchy roots (e.g. potatoes), cereals and grains, nuts and pulses (e.g. peanuts, soybeans, sunflower seeds). Lower concentrations of cadmium are found in meat and fish, with the exception of certain shellfish (e.g. oysters), and certain organ meats (e.g. kidney and liver), which concentrate cadmium. Weekly dietary intake estimates in the EU are in the range of 1.9–3.0 μg/kg body weight (mean, 2.3 μg/kg body weight) for non-vegetarians. Vegetarians, regular consumers of bivalve mollusks, and wild mushrooms are, respectively, estimated to have weekly dietary cadmium exposures of 5.4 μg, 4.6 μg, and 4.3 μg (per kg of body weight). On a body weight basis, estimated cadmium intakes are generally higher for infants and children than for adults.”
Also of interest – “The dietary exposure of Finnish 3-year-old and 6-year-old children to cadmium, lead, arsenic and mercury was determined using concentration data from Finland and individual food consumption data as well as individual weights of the children. 88% of the 3-year-olds and 64% of the 6-year-olds exceeded the tolerable weekly intake of cadmium. Exposure to cadmium and lead was significantly higher for the boys than for the girls in both age groups, and exposure to inorganic arsenic was significantly higher for the 6-year-old boys than the girls of same age.
Ref: Dietary heavy metal exposure of Finnish children of 3 to 6 years
Primary exposure routes of Cadmium
“The primary use of cadmium, in the form of cadmium hydroxide, is in electrodes for Ni–Cd batteries. Because of their performance characteristics like high cycle lives, excellent low- and high-temperature performance, Ni–Cd batteries are used extensively in the railroad and aircraft industry (for starting and emergency power), and in consumer products e.g. cordless power tools, cellular telephones, camcorders, portable computers, portable household appliances and toys.
Cadmium sulfide compounds (e.g. cadmium sulfide, cadmium sulfoselenide, and cadmium lithopone) are used as pigments in a wide variety of applications, including engineering plastics, glass, glazes, ceramics, rubber, enamels, artists colours, and fireworks. Ranging in colour from yellow to deep-red maroon, cadmium pigments have good covering power, and are highly resistant to a wide range of atmospheric and environmental conditions.
Cadmium and cadmium alloys are used as engineered or electroplated coatings on iron, steel, aluminium, and other non-ferrous metals. They are particularly suitable for industrial applications requiring a high degree of safety or durability (e.g. aerospace industry, industrial fasteners, electrical parts, automotive systems, military equipment, and marine/offshore installations) because they demonstrate good corrosion resistance in alkaline or salt solutions, have a low coefficient of friction and good conductive properties, and are readily solderable.
Cadmium salts of organic acids (generally cadmium laurate or cadmium stearate, used in combination with barium sulfate) were widely used in the past as heat and light stabilizers for flexible polyvinyl chloride and other plastics. Small quantities of cadmium are used in various alloys to improve their thermal and electrical conductivity, to increase the mechanical properties of the base alloy (e.g. strength, drawability, extrudability, hardness, wear resistance, tensile, and fatigue strength), or to lower the melting point. The metals most commonly alloyed with cadmium include copper, zinc, lead, tin, silver and other precious metals. Other minor uses of cadmium include cadmium telluride and cadmium sulfide in solar cells, and other semiconducting cadmium compounds in a variety of electronic applications.
In recent years, the use of cadmium for pigments, stabilizers, and coatings purposes has declined, mainly due to concerns over the toxicity of cadmium, and the introduction of regulations, particularly in the European Union, restricting its use.”
Cadmium occurs naturally
“Cadmium occurs naturally in the earth’s crust in association with ores containing zinc, lead, and copper. It is also found naturally in ocean water and air. It is released via volcanic activity, weathering of cadmium-containing rocks, sea spray and forest fires. Elemental cadmium is a soft, silver-white metal, which is recovered as a by-product of zinc mining and refining. The average terrestrial abundance of cadmium is 0.1–0.2 mg/kg, although higher concentrations are found in zinc, lead, and copper ore deposits. Naturally occurring cadmium levels in ocean water range, on average, from < 5 to 110 ng/L.
Man-made sources of cadmium include the mining and smelting of zinc-bearing ores, the combustion of fossil fuels, waste incineration, and releases from tailings piles or municipal landfills, non-ferrous metal production and fossil fuel combustion, followed by ferrous metal production, waste incineration, and cement production.”
Cadmium gets into our water.
“Cadmium enters the aquatic environment from agricultural and urban run-off and atmospheric fall-out and other point sources. Weathering and erosion of cadmium-containing rocks result in the release of cadmium to the atmosphere, the soil and the aquatic system. Sources include non-ferrous metal mining and smelting (from mine drainage water, waste water, tailing pond overflow, rainwater run-off from mine areas), plating operations, phosphate fertilizers, sewage-treatment plants, landfills, and hazardous waste sites. Hence, mine/smelter wastes, commercial fertilizers derived from phosphate ores or sewage sludge, municipal waste landfills contribute to the levels of cadmium found in soil and sediments.
From here Cadmium gets into our food
Wet or dry deposition of atmospheric cadmium on plants and soil can lead to cadmium entering the food-chain through foliar absorption or root uptake. The rate of cadmium transfer depends on a variety of factors, including deposition rates, type of soil and plant, the pH of the soil, humus content, availability of organic matter, treatment of the soil with fertilizers, meteorology, and the presence of other elements, such as zinc.
Reported sediment concentrations of cadmium range from 0.03–1 mg/kg in marine sediments to as high as 5 mg/kg in river and lake sediments. Relatively high concentrations of cadmium (1 mg/kg) have been measured in the soil near smelters and other industrialized areas.”
Cadmium at Work
The main route of cadmium exposure in the occupational setting is via the respiratory tract, although there may be incidental ingestion of dust from contaminated hands, and food. Occupations in which the highest potential exposures occur include cadmium production and refining, Ni–Cd battery manufacture, cadmium pigment manufacture and formulation, cadmium alloy production, mechanical plating, zinc smelting, brazing with a silver–cadmium–silver alloy solder, and polyvinylchloride compounding.
For more details on historical occupational and general exposures to cadmium, see Beryllium, Cadmium, Mercury, and Exposures in the Glass Manufacturing Industry and Cadmium & other metals, Fibres and Dusts
Other industries in which exposure occurs include: foundries, commercial and industrial machinery manufacturing, motor vehicle parts manufacture, architectural and structural metal manufacturing, non-ferrous metal (except aluminium) production and processing, metalworking machinery manufacturing, iron and steel mills and ferro-alloy manufacturing, alumina and aluminium production and processing, and other electrical equipment and component manufacture.
Health effects of Cadmium
Kidney Health Effects
“Upon absorption in the blood, cadmium binds to albumin and is transported to the liver. Cadmium-induced liver damage increases hepatic enzymes Metallothionein (MT), a low molecular weight metal-binding protein, binds cadmium where it is either stored in this conjugated form in the liver or transported to the kidney. Once filtered through the renal glomerulus, the cadmium-MT complex is reabsorbed in the proximal tubules and degraded to release free cadmium. It is this reactive cadmium ion that contributes to renal tubular toxicity while accumulating in the cortex of the kidney. Renal tubule damage is a hallmark of cadmium toxicity and is reflected in increased concentrations of biomarkers such as β2-microglobulin. Glomerular damage may follow with corresponding increased levels of albumin and transferrin.
Urinary cadmium concentration of less than 2.5 μg/g creatinine has been considered to represent safe exposures. However, recent studies have identified increased risk to cancer and mortality following chronic, low-level cadmium exposure. Cancers primarily of the lung, but also prostate, kidney, and pancreas have been documented. A disease unique to cadmium exposure, Ouch Ouch disease, is characterized with severe osteomalacia and osteoporosis from the long-term consumption of cadmium-contaminated rice but has implications for aging patients in general who are diagnosed with osteoporosis.” REF: Deborah E. Keil, Jennifer Berger-Ritchie, Gwendolyn A. McMillin; Testing for Toxic Elements: A Focus on Arsenic, Cadmium, Lead, and Mercury, Laboratory Medicine, Volume 42, Issue 12, 1 December 2011, Pages 735–742, https://doi.org/10.1309/LMYKGU05BEPE7IAW
Hearing Loss and Cadmium
There is mounting evidence that lead and cadmium affect hearing ability.
Studies conducted in the US have already suggested the possibility of hearing impairment in adolescents and adults following lead and cadmium exposure at a level below their respective recommended thresholds.
The ototoxicity (having a toxic effect on the ear or its nerve supply) mechanism involving cadmium is suggested by only a handful of studies. In a study with rats exposed to water containing cadmium, it was shown that cadmium produces reactive oxygen species in auditory cells and causes loss of mitochondrial membrane depolarization, release of cytochrome c, activations of apoptosis and caspases, and an increase in extracellular signal-regulated kinase activation that ultimately elevates the hearing threshold.
A study with US adolescents reported a significant relationship between urinary cadmium and low-frequency hearing impairment. In a study with US adults, there was a significant correlation between blood cadmium levels. However, no significant relationship was found between cadmium and hearing impairment in a study of a Korean population and the article lists reasons why.
Additionally, Chronic otitis media (COM) is caused by an infection of the middle ear, although it may also be associated with environmental pollutants. Recent reports found that cadmium exposure could be toxic to middle ear cell line and indeed environmental cadmium exposure is associated with increased risk of COM. Ref: Environmental cadmium exposure is associated with elevated risk of chronic otitis media in adults
Mercury (Hg), cadmium (Cd), lead (Pb) and antimony (Sb) are toxic trace elements associated with negative health effects on the nervous, renal, cardiovascular and immune system. Element interactions may also amplify the effect of even low dose concentrations.
The half- lives of the elements vary from 3 months for Hg , 2.7 years for Sb , while Pb and Cd have half-lives of about 30 years, so body stores tend to increase with age. Exposure to heavy metals during fetal life and infancy is associated with impairment of growth and central nervous system development, as well as pulmonary and nephrotic damage, and may have serious long-term health consequences for the child. There are limited data on fetal exposure of Sb, but higher levels of Sb are reported in cord blood of pregnancies with an adverse outcome. Ref: Predictors of mercury, lead, cadmium and antimony status in Norwegian never-pregnant women of fertile age
“Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder that affects cognitive and higher cognitive functions. Increasing prevalence of ASD and high rates of related comorbidities has caused serious health loss and placed an onerous burden on the supporting families, caregivers, and health care services. Heavy metals are among environmental factors that may contribute to ASD.”
This study concluded that evaluation of cadmium must be considered for management of ASD patients with neurobehavioral symptoms especially for those who suffer a massive exposure to cadmium (direct and indirect smoking or living in cadmium affected areas).
To date, few studies have investigated the possible correlation between heavy metal status and severity of ASD. Among different toxic metals measured, the urinary excretion of antimony and lead were well correlated with severity of ASD. As well, study demonstrated direct relationships between specific ASD symptom subscales and hair toxic metals (lead, mercury, nickel, and uranium). When assessing toxic metals in blood or erythrocyte, cadmium and mercury showed positive associations with severity of ASD. Interestingly this study found people with ASD in developed countries, but not in developing countries, had lower hair levels for cadmium compared with controls. The extent to which toxic metals might contribute to severity of ASD remains an open problem for further research. Ref: Systematic review and meta-analysis links autism and toxic metals and highlights the impact of country development status: Higher blood and erythrocyte levels for mercury and lead, and higher hair antimony, cadmium, lead, and mercury
Equally disturbing are the very recent findings of 2 studies by Kippler et al. While their previous study indicated that both girls and boys were affected by cadmium, the present evaluation at 10 years of age indicated positive associations of urinary cadmium concentrations with the risk of learning disabilities and the need of special education were more pronounced in boys than girls. The findings provide the strongest evidence of adverse effects of cadmium on brain development.Ref:Cadmium exposure and cognitive abilities and behavior at 10 years of age: A prospective cohort study
A study has shown cadmium exposure in a mother might induce preterm birth. While the placenta is known to accumulate cadmium, it is not known if this may cause placental toxicity and disturbance of fetal development. However a significant relation was found between cadmium concentration of breast milk and maternal urinary cadmium, which showed the existence of maternal-fetal transfer of cadmium by breast milk. Ref: Effects of maternal exposure to cadmium on pregnancy outcome and breast milk
Additionally, “the importance of knowing the concentration of metals in the hair as a biomarker of heavy metal exposure in early stages such as gestation is to be able to prevent alterations in the state of health in later stages. Data suggest that some metals can be transferred to the fetus during pregnancy, indicating a similar level of exposure between mothers and newborns. Additionally, some metals are able to cross the placenta more easily, which is why they are found in a greater proportion in newborns, possibly due to the characteristics of each metal. Comment, the hair analysis can be a good indicator of the exposure during pregnancy; offering the advantage that by knowing the concentration of elements in the hair of the pregnant mother, the exposure of the developing child can be estimated.” REF: Evaluation of the transfer of metals during pregnancy from mother to baby, using newborn hair as an exposure biomarker
And finally – with food as the main route of cadmium exposure for the general population, a recent study showed that the Cadmium tolerable weekly intake, based on potential nephrotoxicity effects, is exceeded by a high proportion of children under 3 years old. Nephrotoxicity results from the accumulation of cadmium in the kidney and appears typically after long-term exposure (40–50 years). Despite the exceeding of the tolerable weekly intake observed during the first three years of childhood, due to low body weights compared to adults, the accumulation rate of cadmium is much lower during the whole childhood period (from 0 to 17 years of age) than during adulthood. These data suggest that dietary exposure to cadmium should be reduced for both children and adults to prevent health concerns associated with nephrotoxicity in later life. Moreover, recent literature suggests that Cadmium can induce other adverse health effects (especially endocrine disruption or neurotoxicity) that could be triggered at even lower doses than those triggering nephrotoxicity. Ref: Dietary exposure to cadmium and health risk assessment in children – Results of the French infant total diet study