Case Study: Chromite mining and processing April 2015 About case studies Background to the request The Environmental and Occupational Health A request was made to Public Health Ontario team provides scientific and technical advice for scientific input on four issues pertaining to and support to the health care system and the chromite mining: Government of Ontario. We have created the broad potential health effects related to Case Study series to share the diverse chromite mining and processing beyond environmental health issues we have concerns arising from chromium exposure encountered and encourage dialogue in these areas. sensitization to chromium mitigation strategies to prevent exposure This response was originally produced in July 2014. The specifics about the location and environmental fate and transport of requestor involved have been removed. chromium The following was selected as a Case Study to Methods illustrate an assessment of a major potential Standard reference textbooks were consulted1–4 industry in Ontario. as well as the scientific databases Scopus and PubMed through searches using the keywords “chromite mining”, “health”, “chromium For more information on Case Studies, please contact us at [email protected]. Visit our website for more from this series. (sensitivity or dermatitis or allergy) mining”, type of compound.8 Chromium (VI) can be “chromium (sensitivity or dermatitis or allergy) acutely toxic at oral chromate doses of around occupational”, and “ferrochrome”. Google 50-70 mg/kg body weight which are vastly Scholar and the Google search engine were also greater than would be expected in a properly used for relevant documents. Relevant controlled workplace.1 Toxic effects after references of articles were also reviewed. ingestion include vomiting and corrosive damage to the gastrointestinal tract which can Chromium result in serious bleeding. After absorption, damage to the liver, kidneys and blood-forming Chromium can exist in a number of valence tissues can ensue.1 states, of which the trivalent (+3 or III) and hexavalent (+6 or VI) states are the most stable. The human carcinogenicity of chromium (VI) is Chromium (III) compounds have some well established. It is classified by the commercial uses, but chromium (VI) has the International Agency for Research on Cancer widest application due to its uses as an acid, (IARC) as a Group 1 agent, or “Carcinogenic to oxidant, and as a colouring agent. Canada humans”.6 IARC’s assessment was based on imported approximately 74,000 tonnes of many studies that indicate a risk of lung cancer chromium-containing products in 1991.5 in workers exposed to chromium (VI) through Chromium (VI) is used to make pigments for inhalation, especially those involved in dyeing textiles, tanning leather and colouring chromate and chromate pigment production glass. Chromium is used widely for and electroplating. A possible risk of nose and electroplating and for making alloys, including nasal sinus cancers was found to have weaker stainless steel.2,6 It also has uses in wood grounding in evidence.6 IARC’s Group 1 includes preservation and corrosion control.1,2 113 different hazards; among these are tobacco smoke, asbestos, sunlight, and wood dust. IARC Chromium and health classifies compounds of chromium (III) and metallic chromium as a Group 3 agent, “Not Chromium (III) is an essential nutrient that classifiable as to its carcinogenicity”.10 enhances insulin’s action and may be directly involved in carbohydrate, fat and protein Ulcerations due to contact with chromium (VI), metabolism.7 Small amounts of chromium are particularly through broken skin and mucous available in many foods, including meat, whole- membranes, were common occupational grain products, fruit and vegetables; however, it injuries prior to modern application of is poorly absorbed orally, with less than 2 per appropriate workplace precautions.1,2,8 These 1,7,8 cent of dietary chromium absorbed. The ulcers most often developed on the extremities a Adequate Intakes for chromium in men and of workers after exposure. Chrome ulcers are women 19-50 years of age are 35 µg/day and 25 due to the direct toxic effect of chromium (VI) 9 µg/day, respectively. rather than an allergic reaction to chromium, which is described below and occurs only in Hexavalent chromium is the form of chromium sensitized individuals.11 Any exposed individual most hazardous for human health, and is largely is susceptible and the occurrence of ulcers does produced by human activities.1,2,6 Chromium not correlate with sensitization in the same (VI) is generally more readily absorbed than person. Neither the mechanism nor the chromium (III), but the rates depend on the minimum exposure concentration and time for ulcer development is known, although a An Adequate Intake is determined when there is concentrations as low as 20-25 mg/L may be insufficient evidence to establish a Recommended sufficient.11 The ulcers heal slowly and usually Dietary Allowance, which is the average daily intake 2,11 that meets a nutrient requirement of nearly all (97 leave a scar. to 98 per cent) healthy individuals.7 Case Study: Chromite mining and health concerns 2 Sensitization to chromium Environmental fate and transport Very little information on chromium sensitivity Based on the facilities that report chromium among miners and ferrochromium workers was releases to Canada’s National Pollutant Release available in English in the published literature. Inventory (NPRI), release to land is the However, dermatitis (skin inflammation) from dominant form of discharge of chromium and contact with chromium has been reported in its compounds to the environment. Of 11 tons cement workers11 and those working with of total onsite releases from the listed facilities, plaster, leather, and metals.2 Chromium 2.4 tons were emitted to air, 0.106 ton was compounds are poorly absorbed through the released to water, and 4.0 tons were released skin .11 However, the hexavalent form is to land.13 This does not include chromium or reduced to its trivalent state upon penetration chromium compounds intended for disposal or of the skin, and it is probably trivalent recycling. chromium that ultimately causes dermal sensitization.11 In most soils, chromium will be present in the trivalent form, which has low solubility and is Chronic work-related skin contact with generally not mobile or reactive. Chromium in chromium in susceptible individuals can lead to plants is mostly retained in the root system.8 allergic contact dermatitis (ACD).11 Once Releases of chromium and its compounds to sensitized, the condition remains for life.11 surface water make up less than 1 per cent of Upon re-exposure to the allergen, individuals total environmental releases in Canada, based with ACD develop redness at the site of on NPRI data from 2013.13 Total dissolved exposure on which a blistering or non-blistering chromium in Great Lakes water samples have rash forms.4 Chronic lesions are characterized ranged from 0.08-0.77 µg/L.5 Chromium will by thickening and scaling of the skin. Although persist in fresh water for up to 18 years and the reaction is generally confined to the area of moves into sediment.8 direct exposure to chromium, strongly sensitized people can develop lesions that are About 60 to 70 per cent of all chromium generalized or spread elsewhere.4 Dermatitis or releases to the atmosphere are due to human activities, of which about one-third is asthma symptoms in response to ingested or 8 inhaled chromium in people with an allergy to hexavalent chromium. Sources of chromium chromium have also been documented.11,12 emissions to air include coal and oil combustion (primarily trivalent), chrome plating Based on surveys of some European countries, (hexavalent) and industrial cooling towers about 4 to 5 per cent of cement workers are (hexavalent).8 Chromium is removed from the estimated to have chromium ACD; however, atmosphere by fallout and precipitation over higher prevalences (13 to 40 per cent) have about 10 days.8 Smoking can contribute to been seen in Poland, Singapore and Taiwan.11 chromium levels in indoor air as tobacco This may be related to different amounts of contains chromium. An air quality study done in chromium present in cement or differences in Windsor in 1991 and 1992 found the average working conditions in these countries.11 chromium concentration was 2.5ng/m3 indoors Shelnutt et al. estimated that 0.52 per cent of and 1.6 ng/m3 outdoors, although the the general United States population is allergic difference was not statistically significant.14 to chromium.11 Case Study: Chromite mining and health concerns 3 Human exposure People who are exposed to chromium occupationally can be exposed to levels of Although humans are exposed to chromium chromium that are up to 100 times higher than through air, water, food or supplements the general population.8 CAREX Canada containing chromium, the primary exposure estimates that about 104,000 Canadians, source for the general population is food.8 including almost 40,000 Ontarians, are Foods that contain chromium include canned occupationally exposed to hexavalent fruit and vegetables, frozen vegetables, meats, chromium (VI).15,16 The largest occupational seafood and eggs.8 Chromium does not groups exposed in Canada are welders, biomagnify in the aquatic or terrestrial food machinists and automotive technicians.15 chain. Where drinking water contains chromium Industries that have been associated with in concentrations greater than 25 µg/L,