ENVIRONMENTAL TOXICOLOGY OF CHROMIUM EM/2012/017 A.L. Savinda Heshani OUTLINE • Properties and oxidation states • Essentiality of Chromium • Potential sources • Exposure routes • Toxicokinetics • Mechanisms of toxicity and carcinogenicity • Toxic symptoms • Standards and regulations for Chromium • Historical cases of poisoning PROPERTIES OF CHROMIUM • Chromium is a hard, steel-gray metal highly resistant to oxidation even at high temperatures. • one of the most abundant metals in the earth’s crust, combined with iron and oxygen in the form of chromite ore (FeCr2O4). OXIDATION STATES OF CHROMIUM • series of oxidation states from −2 valence to +6. Elemental Chromium (0) Trivalent Chromium (+3) Hexavalent Chromium (+6) ESSENTIALITY OF CHROMIUM • Chromium (III) is considered as an essential metal. • Biologically active Cr(IlI) facilitates the action of insulin. • Chromium deficiency results in impaired glucose tolerance. • The estimated safe and adequate daily dietary intake for adults and adolescents is 50-200 /µg/day (National Research Council, Food and Nutrition Board, Washington, DC,1989) • The daily minimum population mean intake ~33 μg/person (WHO) • Adequate Intakes (AIs) for Chromium Source: Institute of Medicine, Food and Nutrition Board, Washington, DC, 2001. SOURCES OF CHROMIUM • Natural sources • chromite ore is in the trivalent state (FeCr204) • Marine/ terrestrial volcanic eruption • Anthropogenic sources 3 basic industries metallurgical chemical and refractory (heat-resistant applications) • In the metallurgical industry -Metal joint prostheses used in clinical orthopedics • In the chemical industry - primarily in paint pigments - chrome plating - leather tanning - wood treatment • Smaller amounts are used in - water treatment - catalysts - safety matches - copy machine toners - corrosion inhibitors - photographic chemicals - magnetic tapes • Refractory uses of chromium include -magnesite-chrome firebrick - granular chromite EXPOSURE ROUTES OF CHROMIUM • The entry routes of chromium into the human body are; -inhalation (Inhalation of chromium-containing aerosols) -ingestion (contaminated food and water) -dermal absorption (contact) TOXICOKINETICS OF CHROMIUM • Major factors governing the toxicity of chromium compounds are; -oxidation state -solubility -nature of its ligands • Toxicity of Chromium (VI) compounds > Chromium(III) compounds • This differing toxicity may be related to -permeability of Cr (VI) through cell membranes -subsequent intracellular reduction to reactive intermediates Cellular uptake and reduction of Chromium compounds • The bronchial tree is the primary target organ for carcinogenic effects of chromium(VI). • Following oral exposure, absorption of chromium in the gastrointestinal tract is low. • In the stomach, Chromium(VI) Chromium(III) • Chromium(III) and chromium(VI) can penetrate human skin to some extent, especially if the skin is damaged. • Chromium transported by the blood is distributed to other organs, the most significant retention being found in the spleen, liver and bone marrow. MECHANISMS OF TOXICITY AND CARCINOGENICITY • In both animals and humans, elimination of absorbed chromium from the body is biphasic, - rapid phase (clearance from the blood) - slower phase (clearance from tissues) • Primary route of elimination – urinary excretion (~50%) • Minor routes - faecal excretion (5%) - bile - transfer to hair and nails - sweat • The remaining chromium is deposited into deep body compartments, such as bone and soft tissue. • The estimated half-life for whole-body chromium elimination chromium(VI) – 22 days chromium(III) – 92 days TOXIC EFFECTS OF CHROMIUM • In general, chromium(VI) compounds are more toxic than chromium(III) compounds. • Health effects of chromium compounds can vary with route of exposure, with certain effects specific for the portal of entry. • Acute poisoning • chronic poisoning oral route mainly from inhalation or skin contact • Effects of chromium are not limited to the portal of entry, hematological, immunological, and reproductive systems also identified as targets for chromium. Chromium (VI) • The primary effects associated chromium(VI) compounds are; -respiratory -gastrointestinal -dermal -immunological -hematological -reproductive -developmental with exposure to • Respiratory effects • Acute exposure causes; nasal and lung irritation, altered pulmonary function, dizziness, headache, coughing, wheezing, sneezing • Intermediate-and chronic exposure causes; epistaxis, chronic rhinorrhea, nasal itching and soreness, nasal mucosal atrophy, perforations and ulceration of the nasal septum, bronchitis, pneumoconiosis, decreased pulmonary function, and pneumonia Perforation of the nasal septum from Chromium(VI) exposure • Gastrointestinal effects • Acute exposure causes; abdominal pain, vomiting, gastrointestinal ulceration, hemorrhage and necrosis, and bloody diarrhea. • Chronic exposure causes; oral ulcer, diarrhea, abdominal pain, indigestion, and vomiting, epigastric pain, irritation, and ulceration • Dermal effects • Acute exposure causes; skin burns • Skin contact with chromate salts may cause; irritation, burns, allergic type of dermatitis rashes, untreated ulcers or sores • Renal effects -Acute Cr (VI) exposure - renal tubular necrosis -Chronic exposure results in transient renal effects • Hepatic effects -Acute chromium exposure - hepatic necrosis • Hematological effects -microcytic -hypochromic anemia • Characterized by -decreased mean cell volume (MCV) -mean corpuscular hemoglobin (MCH) -hematocrit (Hct) -hemoglobin (Hgb) • Reproductive effects -effects on male reproductive organs decreased sperm count and motility histopathological change to the epididymis -effects on females complications during pregnancy and childbirth(toxicosis and postnatal hemorrhage) • Immunological effects -Chromium sensitization • Developmental effects • No studies regarding developmental effects in humans after exposure to chromium compounds. • A number of oral exposure animal studies have shown -postimplantation loss -decreased number of live fetuses -decreased fetal weight -internal and skeletal malformations -delayed sexual maturation in offspring • Genotoxic effects -DNA strand breaks -chromosome aberrations -increased sister chromatid exchange -unscheduled DNA synthesis -DNA-protein crosslinks • Carcinogenic effects -increased risk of respiratory system cancers, primarily bronchogenic and nasal -increased incidence of liver, lung, and kidney and urogenital organ cancers • According to the International Agency for Research on Cancer (IARC); - Chromium[VI] is carcinogenic to humans (Group 1) -Metallic Chromium and Chromium[III] compounds are not classifiable as to their carcinogenicity to humans (Group 3) • According to USEPA; -Chromium(VI) - known human carcinogen by the inhalation route of exposure. EFFECTS OF CHROMIUM ON PLANTS • Chromosomal abberations • Disruption of mitosis • Cell cycle arrest • Polyploidization • Reduced seed germination • Chloroplast disorganization • Reduced photosynthesis • Decreased chlorophyll • Decreased nutrient uptake, water potential • Changes in enzymatic activities • DNA damage • Inhibition of electron transport processes EFFECTS OF CHROMIUM ON AQUATIC ORGANISMS • Chromium toxicity depends on biotic and abiotic factors. • Biotic factors consist of -age -developmental phase of an individual -type of species • Abiotic factors comprises -concentration -oxidation state of Cr -temperature -pH -alkalinity -hardness STANDARDS AND REGULATIONS FOR CHROMIUM EXPOSURE AGENCY ACGIH FOCUS LEVEL Air-Workplace 50µg/m3 NIOSH Air-Workplace 1 µg/m3 COMMENTS Advisory; TWA to avoid carcinogenic risk from certain insoluble chromium compounds Advisory; TWA (10-hour) for carcinogenic Cr (VI) salts 25 µg/m3 TWA (10-hour) for noncarcinogenic Cr (VI) salts, including chromic acid 50 µg/m3 15-minute ceiling limit for noncarcinogenic Cr (VI) salts Continued…… OSHA Air-Workplace 100 µg/m3 Regulation; PEL for chromic acid and chromates (ceiling) 500 µg/m3 PEL for soluble chromic salts (8-hour TWA) 1000 µg/m3 PEL for chromium metal and insoluble salts (8-hour TWA) EPA AirN/A Environment Drinking-Water 50 µg/L Under review Regulation; current MCL for total chromium; proposed MCL is 100 µg/L SRI LANKAN STANDARDS • According to gazette extraordinary of the democratic socialist republic of Sri Lanka - 01.02.2008 • Tolerance limits for the discharge of Parameter Industrial effluents in to inland surface waters Unit type of Tolerance limit Limit values Chromium, total (as Cr) mg/1, max. 0.5 Chromium, Hexavalent (as Cr6+) mg/1, max. 0.1 Industrial waste discharged on land for irrigation purpose Chromium , total (as Cr) mg/1, max. 1.0 Industrial and domestic waste discharged into marine coastal areas Chromium, total (as Cr) mg/1, max. 2.0 Chromium, Hexavalent (as Cr6+) mg/1, max. 1.0 Continued…… Parameter Waste from textile industry being discharged Chromium total (as Cr) into inland surface waters Hexavalent Cr+6) Chromium Waste from being discharged from tanning Chromium total (as Cr) industries - to inland surface waters Hexavalent Cr+6) To marine and coastal areas Chromium Chromium total (as Cr) Hexavalent Cr+6) Chromium Effluents into public sewers with central Chromium total (as Cr) treatment plants Unit type of limit Tolerance Limit values mg/1, max. 2.0 (as mg/1, max. 0.5 mg/1, max. 0.5 (as mg/1, max. 2.0 mg/1, max. 0.5 (as mg/1, max. 2.0 mg/1, max. 2.0 HISTORICAL POISONING OF CHROMIUM Hinkley groundwater contamination • Hinkley groundwater contamination refers to Pacific Gas and Electric Company (PG&E) dumping "roughly 370 million gallons" of chromium-tainted wastewater" into unlined wastewater spreading ponds around the town of Hinkley, California, located in the Mojave Desert from 1952 to 1966 and the ongoing process of restitution and clean-up. • PG&E used chromium VI one of the cheapest and most efficient commercially available rust suppressors in their compressor station for natural gas transmission pipelines. • Just north of California State Highway 58, the residents continue to face concerns over chromium (VI) in their well water from the world's largest plume of this cancer-causing chemical. • Samples taken in August 2010 showed that the plume of contaminated water had started to migrate into the lower aquifer. • As of September 2013, the Cal/EPA reports that the plume has expanded to 6 miles long and 4 miles wide. • In 2015 the California Regional Water Quality Control Board, Lahontan Region served the PG&E with a new order "to cleanup and abate the effects of the discharge of chromium waste or threatened pollution or nuisance." • By the time of the report the plume was "8 miles in length and approximately 2 miles in width, throughout the Hinkley Valley and into Harper Dry Lake Valley. • By 2013 PG&E had spent over $750 million on remediation. Chromium poisoning in Noraiakheda area of Kanpur (2004) • Kanpur was one of the most industrialized towns of Northern India. • These industries have been poisoning the groundwater resources of the town over the years. • The highly polluting industries of Kanpur have rendered the groundwater in their respective areas unsafe and unusable. • The communities are totally dependent on the groundwater for their water needs. • People have no choice but to consume the highly chemicalised and poisoned water. • Noraiakheda is one of the areas in Kanpur where the groundwater has been reported to be heavily contaminated with Chromium and other toxicants. • The groundwater of the area was reported to be laced with high concentration of • Chromium (6.2 mg/l) • Iron (351.8 mg/l) • fluorides (4.2 mg/l) and • pesticides (Lindane 83.47 ng/l, • DDT (192.36 ng/l) for the first time in 1997 by Central Pollution Control Board (CPCB) • The concentrations of Chromium 125 times greater than the desirable limits for drinking water. • People in the area get drinking water through hand and submersible pumps from a depth of 60 ft to 120 ft that is absolutely unsafe for drinking. • Some of the hand pumps spew yellowish and greenish water. • Health effects are clearly visible amongst the local population. • The symptoms of chromium poisoning have started surfacing and undoubtedly an epidemic is under way. • People are afflicted with various skin problems and stomach ailments. • The chromium pollution is impacting the public health, the environment and the economy. Yunnan’s chromium trail • 5,000 tonnes of toxic chromium tailings were dumped near a Yunnan reservoir, contaminating water supplies and resulting water pollution killed fish and livestock, endangered the drinking water of tens of millions of people and attracted widespread media attention across China. • Residents of Yuezhou township, Qujing city, are in despair: their well water has turned yellow, their livestock were dying and their crops were withering. • For months, chemical waste illegally dumped near the shores of Chachong Reservoir, in this corner of Yunnan province, south-west China, was quietly poisoning the community's main water supply. • Rainwater, contaminated after falling on piles of poisonous chromium tailings, flowed into the 300,000 m3 reservoir, turning it toxic. • Levels of deadly hexavalent chromium peaked at over 200 times permitted levels. • Three main crops in Yangqiying and Zhaishang villages were affected: -tobacco leaves turned yellow and speckled -rice and corn showed poor growth. • The authorities quickly identified the hazardous waste as chromium tailings dumped by Luliang Chemicals. • This company claims to be Asia's largest producer of the chemical compound menadione, or vitamin K3. • It is also one of Asia's largest manufacturers of chromium salts: each year, it produces tens of thousands of tonnes of them. • Chromium tailings are a waste product from the manufacturing of chromium salts and metallic chromium. • Cleanup Cr(VI) Sodium metabisulfite Cr(III) Alkali Reduced acidity • • • • • • • • • • • • REFERENCES http://www.euro.who.int/__data/assets/pdf_file/0017/123074/AQG2ndEd_6_4Chromium.PDF http://www.sciencedirect.com/science/article/pii/S0379073811004956 https://link.springer.com/chapter/10.1007/978-3-642-79162-8_10 https://www.atsdr.cdc.gov/toxprofiles/tp7-c2.pdf https://www.atsdr.cdc.gov/csem/csem.asp?csem=10&po=11 https://www.nap.edu/read/4795/chapter/23#295 https://www.eea.europa.eu/publications/GH-07-97-595-EN-C2/chapter6h.html http://www.ievbras.ru/ecostat/Kiril/R/Ecotox/Leo%20Posthuma,%20Glenn%20W.%20Suter%20II,%2 0Theo%20P.%20Traas-Species%20Sensitivity%20Distributions%20in%20EcotoxicologyCRC%20Press%20(2001). http://www.oregon.gov/deq/Rulemaking%20Docs/cu2016epacrit.pdfpdf http://www.meduniv.lviv.ua/files/kafedry/bioneorgan/Chemistry/Group_VIB/Group_VIB.htm https://www.lenntech.com/periodic/elements/cr.htm http://www.ecofriends.org/reports/043GroundWater.htm THANK YOU!