This is an evolving testament of possible exposures to the toxic form of Chromium (hexavalent chromium). Data comes from researching the current literature and other sources. Thanks to all the scientists, researchers, universities, government departments and investigative journalists for making this data possible and available.
At Toxtest we conduct Hair Analysis that can reveal low-dose chronic exposure to heavy metals. If anyone’s results show, for instance, a higher than the normal result for chromium, then the next logical step would be to establish possible exposure routes.
We are putting together an extensive resource for each heavy metal that is tested, that attempts to outline all possible exposure routes to the heavy metal as is known at this point in time. So far we have Lead, Cobalt and this, Chromium. Cadmium is next.
The reason all this is even necessary is that chromium, like many earth elements, exists in more than one form and some of these forms or species as they are sometimes called, are deadly to us. Chromium has a form called Chromium III orCr (III) or trivalent chromium, that is actually a nutrient for us, but also has a form called hexavalent chromium or Cr (VI) that is cancer causing and toxic in other ways.
As you will see, much of this pernicious hexavalent chromium is anthropogenic (originating from human activity).
Snippets have been taken from each quoted reference that in many ways reveal unique routes of exposure of hexavalent Chromium. Each snippet is cited and an active link provided after each. This list of possible exposure sources in not complete but it is a start. Please contribute your knowledge and experience if you know of other sources.
To draw attention to the basic exposure source we used bolded text.
In general, Cr(VI) compounds are better absorbed through the intestinal mucosa than the Cr(III) compounds. However, due to the actions of stomach acid and other components within the gastrointestinal tract, most of an ingested Cr(VI) dosage is converted to Cr(III). In humans and animals, less than 1% of inorganic Cr(III) and about 10% of inorganic Cr(VI) are absorbed from the gut; the latter amount is slightly higher in a fasting state.
Content source: Agency for Toxic Substances and Disease Registry
What about people on antacids and PPi’s and those generally low in stomach acid ?
According to the Toxics Release Inventory, in 1997 the estimated releases of chromium was 30,862,235 pounds to soil from 3,391 large processing facilities accounted for about 94.1% of total environmental releases
Toxno, Toxtest and Environmental Analysis Laboratory (EAL) at Southern Cross University in Lismore, NSW, Australia, collaborate to provide innovation and an Australian first in hair, water, soil/compost or dust testing of 32 heavy metals and minerals. Our Hair or Water analysis is AU$98. Order forms can be downloaded below.
All results are published (de-identified) online and updated regularly as new health or exposure route information becomes available for each metal/mineral. All results are dynamic, contain instructions, have full support and contain clickable links to current health and exposure information for each metal/mineral.
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For the first time in Australia, human and animal hair testing is available to the public using the absolute latest Perkin Elmer Inductively Coupled Plasma–Mass Spectrometer at Environmental Analysis Laboratories in Lismore, Australia. Instrument detection limits are at or below the single part per trillion (ppt) level for many of substances tested. Because this test and the expertise is now available in Australia, we can keep the cost under $100. Doctors, veterinarians, health practitioners and trainers can utilise these tests for their clients.
Total chromium has been identified in 939 soil and 472 sediment samples collected from 1,036 National Priority Lists (NPL) hazardous waste sites [HazDat 2000].
Chromium waste slag containing potentially hazardous levels of Cr(VI) compounds was used as fill material at more than 160 residential, industrial, and recreational sites. Persons living or working in the vicinity of the sites may have been exposed through inhalation, ingestion, or skin contact with contaminated soils and dusts.
Community exposure from this fill occurred in a variety of ways. Wind erosion of the soil could have made slag particles airborne, increasing the opportunity for inhalation of chromium. Chromium compounds leached by rainwater could have migrated through cracks in soil, asphalt roadways, and masonry walls, forming high-content chromium crystals on their surfaces. In soil and roadways, these particles might have been eroded by wind and foot traffic and carried as chromium-laden dust into homes and workplaces. Children playing in areas where the slag was used as fill might also have been exposed through skin contact with chromium-contaminated dust, dirt, and puddles and /or ingestion of contaminated soil.
Environmental sources of chromium include
- airborne emissions from chemical plants and incineration facilities,
- cement dust,
- contaminated landfill,
- effluents from chemical plants,
- asbestos lining erosion,
- road dust from catalytic converter erosion and asbestos brakes,
- tobacco smoke, and
- topsoil and rocks.
Occupational sources of chromium include
- anti-algae agents,
- chrome alloy production,
- chrome electroplating ,
- copier servicing,
- leather tanning ,
- paints/pigments ,
- porcelain and ceramics manufacturing,
- production of high-fidelity magnetic audio tapes,
- textile manufacturing,
- welding of alloys or steel
“Australian scientists say they have conclusive proof that one of the world’s most popular dietary supplements is converted by the body into a cancer-causing chemical.
A study led by the universities of Sydney and NSW has shown that living cells convert chromium III, a naturally occurring element used as a weight loss and type-2 diabetes treatment, into its “carcinogenic cousin” — hexavalent chromium, the industrial pollutant made notorious by the 2000 movie Erin Brockovich and a 2011 chemical spill near Newcastle.
The claims, published in the German journal Angewandte Chemie, are the latest shot in a longstanding debate over the safety of chromium supplements.”
This report needs further investigation but it is certainly plausible that high supplement intakes of chromium III may end up partially at least converted to chromium VI
Trivalent chromium (the type found in supplements), appears to have toxic effects at concentrations above 20µg/mL in the serum or cells; this toxicity is associated with oxidative damage to DNA. This is the same mechanism by which hexavalent chromium is toxic, except the latter is toxic at much lower concentrations, particularly after inhalation during occupations involving the handling of hexavalent chromium.
More than 70% of chromium in the environment comes from anthropogenic sources, such as non-ferrous base metal smelters, refineries, leather tanning industries, urban storm water runoff,effluent streams from pulp and paper mills and discharges from thermal generating stations. Ferrochromium production is the most important industrial source of atmospheric chromium.
Chromium is mainly used in the metallurgical industry (production of ferrochromium alloys, such as stainless steel, high-speed steel, alloy cast irons and non-ferrous alloys), in electrical applications (copper-chromium), in the automobile industry (chromium alloys in the form of stainless steel components, catalytic converters, chrome trim, and other control and decorative systems) and wood preservation (copper chrome arsenate, allowed in Canada for industrial uses and still used for the treatment of wooden poles; Health Canada, 2005).
Chromium is also used in the production of fungicides, drilling muds, water treatment, textiles, catalysts, synthetic rubies for lasers, chromium dioxide magnetic tapes, clinical medicine (labelling of red blood cells), toner for copying machines, montan wax manufacturing and vitamin K manufacturing and as a mordant in wool dyeing, photography and manufacturing of activated carbon
This is an extensive document from 2015 in Canada. Most details of any publication on Chromium.
Chromium in Drinking Water
Document for Public Consultation
Prepared by the Federal-Provincial-Territorial Committee on Drinking Water
Children may be exposed to chromium via the environment to a greater extent than adults because of higher inhalation and ingestion rates per unit of body weight.
The average concentration of chromium in the urine of children at ages five and younger was reported to be significantly higher than in adults residing near industrial sites where chromium waste was used although it has to be noted that urinary biomonitoring has some limitations due to minor sensitivity to detect low-level exposure and due to variability of individuals.
The Scientific Committee Health and Environmental Risks (SCHER) estimated the following exposure to chromium VI from soil for children. The amounts measured for uncontaminated soil were chosen for best, average and worst case scenarios. As it is known that 10 to 29% of the total chromium in contaminated soils is chromium VI, the SCHER calculated the exposure scenarios based on the assumption, that 20% of the total chromium would be chromium VI.
An amount of 200 mg/d soil ingested by a child9 was chosen for the assessment as well as a body weight of 10 kg10, as small children are most likely to ingest soil. The SCHER also estimated that 10% of the ingested chromium VI might be absorbed from the gut and become bioavailable, taking into account the current knowledge on kinetics of chromium VI and the fact that the gut of small children might be more permeable.
The SCHER is aware of the fact that the assessment performed for the uptake of chromium VI from soil by small children is related to one data source only and may be highly variable depending on different soil compositions and geographical conditions.
Table 1: Exposure assessment for the uptake of chromium VI by children from soil
Chromium VI (20% of chromium total)
Amount of soil ingested
Internal exposure (10% absorption from gut)
Chromium contents in food were reported to range from 20 to 590 μg/kg (EPA, 1985) or from 10 to 1,300 μg/kg (WHO, 2003) with the highest levels in meat, molluscs (with a bioconcentration factor of 9,100 L/kg based on mussel dry weight), crustaceans, vegetables and unrefined sugar.
Dietary intake of total chromium by humans has been estimated to range from 5 to 500 μg/d, with a typical value of approximately 100 μg/d (EPA, 1985). Analysis of samples of bread in Portugal for both total chromium and chromium VI revealed that roughly 10% of the total chromium in bread was chromium VI (Soares et al., 2010). Mean levels of chromium VI in bread were 3.8 and 4.6 μg/kg for white and whole bread, respectively. The authors estimated mean chromium VI intakes of 0.57 and 0.69 μg/d from bread. When evaluating chromium in food and drinking water, EFSA reported that there was a lack of data on the presence of chromium VI in food. Therefore, the EFSA Panel on Contaminants in the Food Chain decided to consider all reported analytical results in food as chromium III.
This is disturbing – sounds like the opposite of the precautionary principle
This assumption was based on the fact that food is a reducing medium, and that oxidation of chromium III to chromium VI would not be favoured in such a medium. However, the Panel also noted that if even a small proportion of total chromium in food was in the form of chromium VI, it could contribute substantially to chromium VI exposure.
Chromium has been detected in breast milk at concentrations of 0.06-1.56 μg/L (Casey and Hambidge, 1984), suggesting that children could be exposed to chromium from breast-feeding mothers. Studies on mice have shown that chromium crosses the placenta and can concentrate in foetal tissue
Sandals seemed to be over-represented among the shoes with detectable chromium VI. The shoe with one of the highest levels of chromium VI content was a child’s sandal.
In a worst case scenario, the dermal exposure to chromium VI from a chromium-leather tanned shoe was calculated to be 0.45 μg/cm2, based on a content of 3 mg chromium VI/kg leather (Danish EPA, 2012).
Contact with copper chrome arsenate (CCA)-treated wood was identified as a source of chromium VI exposure for adults and for children in the EU risk assessment report. A body burden of 1.63 μg/kg bw/d has been calculated, based on the inhalation and dermal exposure values for a typical consumer handling and sawing dry CCA treated timber. For a child playing on CCA-treated timber, a body burden of 0.1 μg/kg bw/d has been estimated for oral ingestion and dermal exposure (ECB, 2005).
For chromated end products with a layer of chromium oxide on the metal surface, up to 15% chromium VI has been measured in the coating (AFSSET, 2008).
Concerning consumer products, leather articles contribute considerably to chromium VI exposure. Surveys of chromium VI in articles of leather in Germany and Denmark have demonstrated that more than 30% of the tested articles contained chromium VI in concentrations above 3 mg/kg (Danish EPA, 2012).
The EU rapid alert system (RAPEX) frequently publishes a list of consumer products exceeding the current limit value for chromium VI, demonstrating the impact of consumer products regarding the exposure of the general public to chromium VI.
Scientific Committee Health and Environmental Risks SCHER
Opinion on Chromium VI in toys
Stainless steel contains up to 20% Cr by weight and is the highest volume product containing this metal. The magnitude of Cr utilization is also evident from the estimated occupational exposure by more than 500,000 workers in the U.S. alone. Incineration and emissions from cars create ambient pollution with small Cr(VI)- and Cr(III)-containing particles, which leads to low-level inhalation exposures by large segments of the general population and increases Cr levels in surface waters.
The most serious cases of anthropogenic contamination of drinking water in the U.S. came from the discharges of toxic Cr(VI) by cooling towers. Other large-scale environmental pollution with Cr(VI) involved improper disposal of millions of tons of incompletely processed chromite ore. Hundreds of the largest toxic waste sites in the U.S. known as Superfund sites contain Cr as a major contaminant.
The presence of Cr(VI) in drinking water can also result from the oxidation of naturally occurring Cr(III) by Mn(III/IV) oxides in birnessite, a common mineral that coats weathered grains and fractures in Cr-rich ultramafic rocks and serpentinites that are enriched with chromite [FeCr(III)2O4]. In addition to birnessite, the presence of two other Mn(IV) oxide-containing minerals, asbolane and lithiophorite, has also been associated with the formation of Cr(VI) from natural Cr(III).
Examination of four minerals made of Mn oxides (birnessite, cryptomelane, todorokite, and hausmannite) showed that birnessite had the highest ability to oxidize Cr(III) under laboratory conditions.
Chromium in Drinking Water: Sources, Metabolism, and Cancer Risks by Anatoly Zhitkovich* Chem Res Toxicol. 2011 Oct 17; 24(10): 1617–1629.
The highest Cr concentration in imported rice on sale in Australia was found in Thai rice followed by Indian (basmati), Bangladeshi and Pakistani (basmati) rice . The mean Cr concentration in Thai rice was 413 mg kg 1 (range: 61– 743 mg kg 1, n1⁄412), which is about double to that in Indian rice (mean: 190 mg kg 1, range: 27–578 mg kg 1, n1⁄415). The mean Cr concentration in Australian grown rice was 144 mg kg 1 (range: 15–465 mg kg 1, n1⁄421) with the highest in white rice (mean: 404 mg kg 1, range: 346–465 mg kg 1, n1⁄43) followed by clever rice and brown rice.
A previous study by Fu et al. (2008) reported mean Cr concentration in Chinese rice of 199 mg kg1 (range: 62–424 mg kg1, n1⁄44), which is higher than that in Australian grown rice. The Cr concentrations in Italian Arborio and Vietnamese Jasmin rice varieties were 55 and 67 mg kg 1, respectively, which are considerably lower than that found in rice of other origin.
Except for radish leaf, Australian grown vegetables with the highest mean Cr concentrations were spinach , eggplant, radish, pumpkin, cabbage. Among the Bangladeshi vegetables, the highest mean Cr concentration was in jute leaf (mean: 695 mg kg 1) followed by green amaranth (mean: 290 mg kg 1, range: 261–319 mg kg 1, n1⁄42) and pointed ground (mean: 120 mg kg 1, range: 97–155 mg kg 1, n1⁄44) (Fig. 3B). A recent study by Rahman et al. (2012a) showed that the mean Cr concentrations in leafy and non-leafy vegetables from Bangladesh were 1120 mg kg 1 (range: 350–4480 mg kg 1) and 640 mg kg 1 (range: 180–1910 mg kg 1), respectively. An earlier study by Karim et al. (2008) reported a much higher concentration of Cr in Bangladeshi vegetables (mean: 27.14 mg kg 1, range: 23.31–33.84 mg kg 1). The results imply that the mean Cr concentration in Bangladeshi vegetables imported into Australia of this study is considerably lower than the mean Cr concentrations detected in Bangladeshi vegetables in other studies.
In Bangladesh, the main sources of Cr in agricultural soils where the farmers grow vegetables are the repeated use of untreated or poorly treated wastewater from industrial establishments (e.g. textile and tannery sludge) and the application of chemical fertilizers and pesticides. Therefore, lower Cr content in Bangladeshi vegetables (on sale in Australia) of the present study than that of the other study (in Bangladesh) may be because the vegetables imported into Australia were grown in a less-contaminated area of Bangladesh. As there is no Australian standard maximum limit for Cr in rice and vegetables, Cr bioavailability is generally low in foodstuffs and similar Cr concentrations to those found in Australian and Bangladeshi foods in the current study have been demonstrated to be beneficial to domestic pigs.
Heavy metals in Australian grown and imported rice and vegetables on sale in Australia: Health hazard Article in Ecotoxicology and Environmental Safety · February 2014 DOI: 10.1016/j.ecoenv.2013.11.024
Major contributors to dietary intake of chromium were bread, cereal, milk, juice, cake, deli meats, chocolate, tea and beer.
Chromium is abundant in the environment and is therefore widely distributed in the food supply. Dietary sources of chromium include meat, fish, legumes, wholegrain cereals, vegetables and yeast. Other sources include egg yolks, spices, cheese, fruits (e.g. apple, orange and pineapple), and peanuts.
Chromium content of foods – The highest levels of chromium was found in the following foods: chocolate and chocolate cake, ham, parsley and salt.
Intakes were similar for boys and girls up to the age of 8 years. After this age, boys consumed larger amounts than girls. There was a large increase with age in males up to 29 years of age and then a pronounced decline with age after 30 years of age. By contrast, there was only a slight decline in mean intake with age among women.
Major contributing foods – Bread, other cereals, milk and juice were major contributors to chromium intakes for all ages from 2 years, with milk contributing greater proportions of the chromium intake of children than of adults.
Infant formula was the major source of chromium in infant diets. For older women, tea contributed approximately 7-13% and for adult males, beer, hamburger meat and delicatessen meats also made important contributions to chromium intake.
In the absence of an Australian UL for chromium, it is unclear whether the current dietary intakes are excessive. However, given that all mean and 95th percentile intakes were well below an intake of 0.15 mg trivalent chromium/kg bw/day (equivalent to 10.5 mg/day for a 70 kg person) concluded by the UK Expert Group on Vitamins and Minerals (2003) to be unlikely to have adverse health effects, it is unlikely that Australian chromium intakes are excessive.
Chromium is used in the manufacture of cars, glass, pottery and linoleum.
Chromium VI which is used on leather and new wool from Are you wearing chemical couture?
All Cr(VI)-containing compounds were once thought to be man-made, with only Cr(III) naturally ubiquitous in air, water, soil and biological materials. Recently, however, naturally occurring Cr(VI) has been found in ground and surface waters at values exceeding the World Health Organization limit for drinking water of 50 μg of Cr(VI) per litre. Chromium is widely used in numerous industrial processes and as a result is a contaminant of many environmental systems . Commercially chromium compounds are used in industrial welding, chrome plating, dyes and pigments, leather tanning and wood preservation. Chromium is also used as anticorrosive in cooking systems and boilers.
It is estimated that more than 300,000 workers are exposed annually to chromium and chromium-containing compounds in the workplace.
Also, the general human population and some wildlife may also be at risk. It is estimated that 33 tons of total Cr are released annually into the environment . The U.S. Occupational Safety and Health Administration (OSHA) recently set a “safe” level of 5μg/m3, for an 8-hr time-weighted average, even though this revised level may still pose a carcinogenic risk . For the general human population, atmospheric levels range from 1 to 100 ng/cm3 , but can exceed this range in areas that are close to Cr manufacturing.
Non-occupational exposure occurs via ingestion of chromium containing food and water whereas occupational exposure occurs via inhalation. Chromium concentrations range between 1 and 3000 mg/kg in soil, 5 to 800 μg/L in sea water, and 26 μg/L to 5.2 mg/L in rivers and lakes . Chromium content in foods varies greatly and depends on the processing and preparation.
Heavy Metals Toxicity and the Environment
*Correspondence to Paul B. Tchounwou. email@example.com, Tel: 601-979-0777 Fax: 601-979-0570.
Chromium compounds have a wide range of water solubilities, but the general rule is that the trivalent chromium salts are almost insoluble and the hexavalent ones are soluble. Hexavalent compounds are reduced to the trivalent form in the presence of oxidisable organic matter such as timber and in living organisms. In living organisms the conversion back to the hexavalent state is considered not to occur (ie. under acidic conditions or by organic matter) due to the high energy required. Trivalent chromium is generally considered to be stable and immobile in soil.
A 1997 UK total dietary survey [as described in a recent European Commission (EC) evaluation of trivalent chromium6] indicated that the highest chromium levels were found in meat products, oils and fats, bread, nuts and cereals.
In major Australian reticulated water supplies, total chromium concentrations range up to 0.03 mg/L, with typical concentrations being less than 0.005 mg/L.
Based on health considerations, the NHMRC has set a Health Guideline Value for chromium in Australian drinking water at 0.05 mg/L. It is recommended that if the concentration of total chromium exceeds this value then a separate analysis for hexavalent chromium should be undertaken.
Risk to humans from exposure to chromium in CCA-treated timber…
Although hexavalent chromium compounds are hazardous to human health by virtue of their carcinogenicity potential it has been shown that sawdust from CCA-treated timber contains between 0.3-0.4% of total chromium and less than 2% of the total chromium was present in the hexavalent form.
Toxicology Assessment – Part 1
Australian Pesticides and Veterinary Medicines Authority (APVMA)
Copper chrome arsenate (CCA) treated timber is wood that has been treated with a preservative containing copper, chromium and arsenic. CCA-treated timber should not be used to build children’s play equipment, patios, domestic decking, handrails, new garden furniture, exterior seating or picnic tables.
As a precaution, you should limit possible exposure to CCA-treated timber chemicals – especially for young children.Never burn CCA-treated timber in fireplaces, barbeques, wood stoves or any wood fire.
Never burn CCA-treated timber in fireplaces, barbecues, wood stoves or any wood fire.
After a bushfire, keep children and pets away from the CCA-treated timber ash until it is removed, and follow safety precautions for clean up.
Although the chemicals are fixed within the dry wood in CCA-treated timber, concerns have been expressed internationally about the potential for harm as small amounts of arsenic can leach out of the surface of the timber.
GHS CARCINOGEN, GERM CELL MUTAGEN AND REPRODUCTIVE TOXICANT CLASSIFICATIONS
The following are some chromium-containing chemicals with carcinogen, germ cell mutagen and reproductive toxicant classifications:
- Chromium (VI) trioxide: Carc. 1A , Muta. 1B, Repr. 2 (Suspected of damaging fertility)
- Zinc chromates including zinc potassium chromate: Carc. 1A
- Ammonium dichromate: Carc. 1B, Muta. 1B, Repr. 1B (May damage fertility, may damage the unborn child)
- Calcium chromate: Carc. 1B
- Chromic oxychloride: Carc. 1B, Muta. 1B
- Chromium-III-chromate: Carc. 1B
- Chromium (VI) compounds, with the exception of barium chromate and of compounds specified elsewhere in Annex VI: Carc. 1B
- Lead sulfochromate yellow [C.I. Pigment Yellow 34]: Carc. 1B, Repr. 1A (May damage the unborn child, suspected of damaging fertility)
- Lead chromate: Carc. 1B, Repr. 1A (May damage the unborn child, suspected of damaging fertility)
- Lead chromate molybdate sulfate red [C.I. Pigment Red 104]: Carc. 1B, Repr. 1A (May damage the unborn child, suspected of damaging fertility)
- Potassium chromate: Carc. 1B, Muta. 1B
- Potassium dichromate: Carc. 1B, Muta. 1B, Repr. 1B (May damage fertility, may damagethe unborn child)
- Sodium chromate (VI): Carc. 1B, Muta. 1B, Repr. 1B (May damage fertility, may damage the unborn child)
- Sodium dichromate: Carc. 1B, Muta. 1B, Repr. 1B (May damage fertility, may damage the unborn child)
- Strontium chromate: Carc. 1B 2:1 mixture of: 4-(7-hydroxy-2,4,4-trimethyl-2-chromanyl)resorcinol-4-yl-tris(6-diazo-5,6- dihydro-5-oxonaphthalen-1-sulfonate) and 4-(7-hydroxy-2,4,4-trimethyl-2-chromanyl) resorcinolbis(6-diazo-5,6-dihydro-5-oxonaphthalen-1-sulfonate): Carc. 2 Trisodium-bis(7-acetamido-2-(4-nitro-2-oxidophenylazo)-3-sulphonato-1-naphtholato) chromate(1-): Muta. 2.
CHROMIUM OCCURRENCE AND SOURCES
Chromium (Cr) is the 17th most abundant element in the Earth’s mantle and naturally occurs as chromite (FeCr2O4) in ultramafic and serpentine rocks or complexed with other metals like crocoite (PbCrO4), bentorite Ca6(Cr,Al)2(SO4)3 and tarapacaite (K2CrO4), vauquelinite (CuPb2CrO4PO4OH), among others.
The anthropogenic sources of Cr in the environment stem from the use of Cr in the metallurgy, refractory and chemical industries.
Chromium from anthropogenic sources can be released to soils and sediments indirectly by atmospheric deposition, but releases are more commonly from dumping of Cr-bearing liquid or solid wastes such as chromate by-products (“muds”), ferrochromium slag, or chromium plating wastes. Such wastes can contain any combination of Cr (III) or Cr(VI) with various solubilities .
For example, H2CrO4 is used for cleaning glassware in chemical laboratories by oxidising organic residues.
The scientific literature suggests that household materials, including some wood stains used in the past, may be a source of hexavalent chromium in household dust.
A Guide to the Hexavalent Chromium in Household Dust Studies Prepared by the New Jersey Department of Environmental Protection
Timbers have been preserved with formulations of Cu, Cr, and As (CCA), and there are now many derelict sites where soil concentrations of these elements greatly exceed background concentrations. Such contamination has the potential to cause problems, particularly if sites are redeveloped for other agricultural or nonagricultural purposes. Compared with fertilisers, the use of such materials has been more localised, being restricted to particular sites or crops.
Chromium is mined as a primary ore product in the form of the mineral chromite, FeCr2O4. Major sources of Cr-contamination include releases from electroplating processes and the disposal of Cr-containing wastes . Chromium(VI) is the form of Cr commonly found at contaminated sites.
The application of numerous biosolids (e.g., livestock manures, composts, and municipal sewage sludge) to land inadvertently leads to the accumulation of heavy metals such as As, Cd, Cr, Cu, Pb, Hg, Ni, Se, Mo, Zn, Tl, Sb, and so forth, in the soil.
It is estimated that in the United States, more than half of approximately 5.6 million dry tonnes of sewage sludge used or disposed of annually is land applied, and agricultural utilisation of biosolids occurs in every region of the country. In the European community, over 30% of the sewage sludge is used as fertiliser in agriculture. In Australia over 175 000 tonnes of dry biosolids are produced each year by the major metropolitan authorities, and currently, most biosolids applied to agricultural land are used in arable cropping situations where they can be incorporated into the soil.
There is also considerable interest in the potential for composting biosolids with other organic materials such as sawdust, straw, or garden waste. If this trend continues, there will be implications for metal contamination of soils. The potential of biosolids for contaminating soils with heavy metals has caused great concern about their application in agricultural practices. Heavy metals most commonly found in biosolids are Pb, Ni, Cd, Cr, Cu, and Zn, and the metal concentrations are governed by the nature and the intensity of the industrial activity, as well as the type of process employed during the biosolids treatment.
Under certain conditions, metals added to soils in applications of biosolids can be leached downwards through the soil profile and can have the potential to contaminate groundwater. Recent studies on some New Zealand soils treated with biosolids have shown increased concentrations of Cd, Ni, and Zn in drainage leachates.
Table 1 : Industries and types of Hexavalent chromium chemicals
Types of Hexavalent Chromium Chemicals
Pigments in paints, inks, and plastics
Lead chromate (PbCrO4) zinc chromate (ZnCrO4) barium chromate calcium chromate potassium dichromate sodium chromate
Anti-corrosion coatings (chrome plating, spray coatings)
Chromic trioxide (chromic acid) zinc chromate (ZnCrO4) barium chromate (BaCrO4) calcium chromate sodium chromate strontium chromate (SrCrO4)
Hexavalent chromium (when cast, welded, or torch cut), Ammonium dichromate ((NH4) 2Cr2O7) potassium chromate potassium dichromate sodium chromate
Ammonium dichromate ((NH4)2Cr2O7)
Chromium (VI) in ground water has generally been assumed to be anthropogenic (manmade) contamination, since it is used in a number of industrial applications, including electroplating, tanning, Industrial water-cooling, Paper pulp production and petroleum refining. Severely infected with cancerous dyes and chemicals from defunct industries, the drinking water has been rendered extremely toxic.
A basic chrome sulfate manufacturing plant for tanneries has left a legacy of chromium,lead, and pesticide (i.e. DDT and Lindane) pollution. Huge amounts of the chemical waste produced here were buried on the grounds of the old plant. This contaminated material has contaminated groundwater, and therefore wells and drinking water.
A 1997 study conducted by the Central Pollution Control Board on the groundwater quality in Kanpur revealed Cr VI levels of 6.2 mg/l; the Indian government places the limit at .05 mg/l. In addition to chromium, the study revealed high concentrations of iron, fluoride, alkalinity, coliform, pesticides, dissolved solids, and hardness.
The tanneries discharge their toxic waste laden with Cr VI into the sewage system. This effluent is carried through the main drainage system to the centralized treatment plant. The treated water is then used for farming irrigation or released directly into the river.
The resulting sludge from the treated wastewater is left to dry on sludge beds and subsequently dumped outside of the treatment plant.
HEXAVALENT CHROMIUM (VI) : ENVIRONMENT POLLUTANT AND HEALTH HAZARD – Journal of Environmental Research And Development Vol. 2 No. 3, January-March 2008
Upper Level of Intake OF CHROMIUM from food and supplementation
The ULs for chromium are unknown as there are insufficient data.
A number of potential adverse effects of high chromium intakes in relation to renal failure, genotoxicity, carcinogenicity, hepatic dysfunction and reproductive function have been seen either in animal studies or in humans. However, adequate human data on trivalent chromium are limited.
No adverse side effects were reported in a number of supplementation trials in which subjects received up to 1 mg chromium/day, mostly as picolinate, for several months. These trials, however, were mainly studies of efficacy and not designed to find potential toxic effects. The limited data from all studies on subchronic, chronic and reproductive toxicity on soluble trivalent chromium salts do not give clear information on the dose-response relationship. Therefore, ULs cannot be derived.
Orthodontic alloys are made from various metals, among which chromium and nickel are of major concern. Both of these genotoxic, mutagenic, and cytotoxic metals might induce contact allergy, asthma, hypersensitivity, birth defects, and reproductive damage. Corrosion of orthodontic alloys might lead to release of considerable amounts of nickel and chromium ions into saliva.
This prospective preliminary study was conducted to evaluate hair nickel and chromium levels in fixed orthodontic patients. Scalp hair nickel/chromium concentrations of 12 female and 12 male fixed orthodontic patients were measured before treatment and 6 months later, using atomic absorption spectrophotometry. The effects of treatment, gender, and age on hair ions were analyzed statis- tically
After 6 months, nickel increased for 387 % (paired t test P = 0.0000) and chromium increased for 16 % (P = 0.0002). No significant correlations were observed be- tween any ion levels with age or gender (Spearman P > 0.2). Within the limitations of this preliminary study, it seems that 6 months of fixed orthodontic treatment might increase levels of hair nickel and chromium. Future larger studies are neces- sary to validate these results.
Effects of Fixed Orthodontic Treatment on Hair Nickel and Chromium Levels: A 6-Month Prospective Preliminary Study – Biol Trace Elem Res (2015) 164:12–17
FROM MINERAL STATUS EVALUATION – Stephen Markus, M.D.
Hexavalent chromium also occurs naturally. Trivalent chromium can be oxidized to hexavalent chromium during water disinfection. Hexavalent chromium compounds are more water soluble than trivalent chromium compounds.
The major source of hexavalent chromium in drinking water is oxidation of naturally occurring chromium present in igneous geologic formations.
Chromium is found naturally in rocks, plants, soil and volcanic dust, humans and animals. Hexavalent chromium is widely found in waters, including source waters for drinking water, at concentrations varying from sub- μg/L levels to more than 100 μg/L.
Hexavalent chromium can naturally occur in waters throughout the United States
The study found that total chromium occurs both in surface and groundwaters; however, hexavalent chromium was not found in surface waters to the same degree as in groundwaters. Total chromium in surface waters, with a few exceptions, was primarily composed of trivalent chromium. A significant fraction of groundwater results showed that the total chromium concentrations were composed exclusively of hexavalent chromium.
Theoretically, up to 100% of total chromium can be present in hexavalent chromium form. However, the actual fraction of hexavalent chromium varies depending on the water type (ground water versus surface water, raw water versus treated drinking water, etc.), geographical location and the oxidation reduction potential of the water.
Chromium in Drinking Water: A Technical Information Primer – American Water Works Association
Chromium-tanned leather is the most popular form of producing leather these days, and one of the most noxious. It relies on a toxic slush of chromium salts and tanning liquor to produce a supple and often light blue colored product. The prepared hides are first pickled in a vat of chromium until the material’s pH drops to 2.8 – 3.2, then they’re transferred to a secondary vat filled with tanning liquor which penetrates the leather.
Once the liquor has been thoroughly and evenly absorbed, the pH of the vat is increased to between 3.8 and 4.2. This fixes the tanning material to the leather at a molecular level and helps reduce the amount of shrinkage experienced when the leather is submerged in warm water.
The tanning industry poses many dangers to both the environment and those that work within it. The primary environmental threat involves the dumping of solid and liquid waste that contains leftover chromium and other hazardous compounds. This is commonplace in regions without strong environmental protection standards, which also happen to be the primary regions where leather is tanned, such as China, India, and Bangladesh.
Even in fully modernised and carefully managed facilities, it is nearly impossible to reclaim all of the pollutants generated by the tanning process.
As a rule of thumb, tanning one ton of hide typically results in 20 to 80 cubic meters of wastewater with Chromium concentrations around 250 mg/L and sulfide concentrations at roughly 500 mg/L, not to mention the offal effluence from the preparation phase and the pesticides often added to keep mold growth down during transport to the facility. Hell, 70 percent of an untreated hide is eventually discarded as solid waste—the hair, fat, meat, sinew, all goes straight into the trash.
Ore refining, chemical and refractory processing, cement-producing plants, automobile brake lining, catalytic converters for automobiles, leather tanneries, and chrome pigments contribute to the atmospheric burden of chromium
Chromium uptake is enhanced in animals when given at the same time as vitamin C . In a study of three women, administration of 100 mg of vitamin C together with 1 mg of chromium resulted in higher plasma levels of chromium than 1 mg of chromium without vitamin.
Compared to diets rich in complex carbohydrates (e.g., whole grains), diets high in simple sugars (e.g., sucrose) result in increased urinary chromium excretion in adults. This effect may be related to increased insulin secretion in response to the consumption of simple sugars compared to complex carbohydrates.
The lack of an accurate measure of chromium nutritional status prevents the identification of individuals who may be susceptible to chromium deficiency. In 2001, the US Institute of Medicine set the adequate intake (AI) of chromium at 20-35 μg/day for adults.
Randomised controlled trials have failed to provide any evidence of benefits of chromium supplementation in the prevention or treatment of impaired glucose tolerance and type 2 diabetes mellitus.
Linus Pauling Institute
Micronutrient Information Center
Chromium (VI) compounds are used widely in applications that include: pigment for textile dyes (e.g. ammonium dichromate, potassium chromate, sodium chromate), as well as for paints, inks, and plastics (e.g. lead chromate, zinc chromate, barium chromate, calcium chromate, potassium dichromate, sodium chromate); corrosion inhibitors (chromic trioxide, zinc chromate, barium chromate, calcium chromate, sodium chromate, strontium chromate); wood preservatives (chromium trioxide); metal finishing and chrome plating (chromium trioxide, strontium chromate), and leather tanning (ammonium dichromate).
Chromium (VI) may be present as an impurity in Portland cement, and it can be generated and given off during casting, welding, and cutting operations (for example, of stainless steel), even if it was not originally present in its hexavalent state
Inhalation of dusts, mists or fumes, and dermal contact with chromium-containing products are the main routes of occupational exposure. Industries and processes in which exposure to chromium (VI) occurs include: production, use and welding of chromium-containing metals and alloys (e.g. stainless steels, high-chromium steels); electroplating; production and use of chromium-containing compounds, such as pigments, paints (e.g. application in the aerospace industry and removal in construction and maritime industries), catalysts, chromic acid, tanning agents, and pesticides
Only lead chromate (as crocoite) and potassium dichromate (as lopezite) are known to occur in nature.
Based on US data collected from 2106 monitoring stations during 1977–84, the arithmetic mean concentrations of total chromium in the ambient air (urban, suburban, and rural) were in the range of 0.005–0.525 μg/m3
Chromium is present in most soils in its trivalent form, although chromium (VI) can occur under oxidizing conditions (ATSDR, 2008a). In the USA, the geometric mean concen- tration of total chromium was 37.0 mg/kg (range, 1.0–2000 mg/kg) based on 1319 samples collected in coterminous soils
Tobacco smoke contains chromium (VI), and indoor air polluted by cigarette smoke can contain hundreds of times the amount of chromium (VI) found in outdoor air.
Occupational exposure in Industry
Based on occupational exposure to known and suspected carcinogens collected during 1990–93, the CAREX database estimates that 785692 workers were exposed to hexavalent chromium compounds in the European Union, with over 58% of workers employed in the following four industries: manufacture of fabricated metal products except machinery and equipment (n = 178329), manufacture of machinery except electrical (n = 114452), personal and household services (n = 85616), and manufacture of transport equipment (n = 82359).
In Canada – Industries in which exposure occurred include: printing and support activities; architectural/structure metal manufacturing; agricultural, construction, mining machinery manufacturing; specialty trade contractors; boiler, tank, and container manufacturing; industrial machinery repair; auto repair; metalworking machinery manufacturing; steel product manufacturing; aluminum production; metal ore mining; coating, engraving, and heat treating. Welders were the largest occupational group exposed (n = 19100 men and 750 women).
CHROMIUM (VI) COMPOUNDS IARC MonoGraphS – 100C
Cement and concrete are products used widely in the construction sector, with a traditional perception that any hazards that they have are limited to dermatitis in a small number of workers. In some cases, employers and builders do not think that concrete is a chemical. However, contact dermatitis is one of the most frequently reported health problems among construction workers. A review of the available literature suggests that cement has constituents that produce both irritant contact dermatitis and corrosive effects (from alkaline ingredients such as lime) and sensitization, leading to allergic contact dermatitis (from ingredients such as chromium).
These findings indicate that cement and concrete should be treated as hazardous materials, and that workers handling such products should reduce exposure wherever possible. Initiatives to reduce the chromium content of cement have been shown to be successful in reducing the incidence of allergic dermatitis, although the irritant form remains.
The dermal toxicity of cement doi: 10.1191/0748233702th159oa – Toxicol Ind Health August 2002 vol. 18 no. 7 321-331
Kooragang Island, New South Wales
Hexavalent chromium was released from the Newcastle Orica explosives plant on August 8, 2011. Up to 20 workers at the plant were exposed and 70 nearby homes in Stockton.
The town was not notified until three days after the release of the hexavalent chromium and the accident sparked a major public controversy, with Orica criticised for playing down the extent and possible risks of the leak, and NSW state environment minister Robyn Parker and her department attacked for their slow response to the incident.
In December 2011, the August 8 leak was the subject of an NSW parliament upper house inquiry, and the NSW Office of Environment and Heritage ordered Orica to undergo an environmental audit, due to be completed by May 2013.
In 2010, the Environmental Working Group studied the drinking water in 35 American cities. The study was the first nationwide analysis measuring the presence of the chemical in U.S. water systems. The study found measurable hexavalent chromium in the tap water of 31 of the cities sampled, with Norman, Oklahoma, at the top of a list; 25 cities had levels that exceeded California’s proposed limit of VI and its less toxic forms.
Hexavalent chromium was found in drinking water in the southern California town of Hinkley and was brought to popular attention by the involvement of Erin Brockovich and Attorney Edward Masry. The f0.58 ppm chromium VI in the groundwater in Hinkley exceeded the Maximum Contaminant Level (MCL) of 50 ppm for total chromium currently set by the United States Environmental Protection Agency (EPA). The source of contamination was from the evaporating ponds of a PG&E (Pacific Gas and Electric) natural gas pipeline compressor station, which were used to dry the precipitate from the cleaning solution for the cooling stacks.
Hexavalent chromium Wikipedia
See some of our Toxtest results and Toxno profile for Chromium.
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