Guidelines for Metals and Metalloids in Ambient ... - ARCHIVE: Defra

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Expert Panel on Air Quality Standards Figure 5.2: Chromium – pulmonary absorption, metabolism & excretion (a) chromium containing particulate matter or fumes may be inhaled (b) hexavalent chromium, Cr(VI), the carcinogenic form of chromium is reduced to Cr (III) by low molecular weight reductants such as ascorbic acid and glutathione in epithelial lining fluid. (c) any remaining Cr(VI) is transported into cells via the anion transport channel along a concentration gradient and (d) inside the cell reacts with reductants which leads to the formation of reactive oxygen species (ROS). The product, Cr(III) is less reactive and is subsequently released into the blood and excreted via the urine (e) involvement of other reductants can lead to carbon and sulphur radical formation that can also lead to tissue damage through oxidation of cellular targets such as proteins and DNA. Cr(VI) a Lung Cell b AA GSH AA . GSSG Cr(VI) Cr(III) c d Cr(VI) Cr(III) AA GSH AA . GSSG Oxidative stress DNA damage Excretion Cr(III) e 5.2.2 Metabolism 250. Any Cr(VI) reaching the blood is taken up by erythrocytes and reduced to Cr(III) by glutathione. Thereafter it may react with other cell components and is gradually released into the circulation where they bind to plasma proteins (USEPA, 1998). 88
Chromium 5.2.3 Tissue distribution and excretion 251. Absorbed chromium travels around the body absorbed to plasma proteins and is taken up by a range of tissues including bone, liver, kidney and spleen (USEPA, 1998). 252. Absorbed chromium is eliminated largely in the urine with most of the unabsorbed portion in faeces (CEPA, 1994). The hair and nails are also minor pathways of excretion (Defra and EA, 2002). 5.3 Health effects 5.3.1 Acute effects 5.3.1.1 Animal studies 253. Trivalent and hexavalent chromium can result in toxicity following oral, inhalation and dermal exposures. Acute oral toxicity in animals increases with increasing water solubility. Oral LD50 ranges for trivalent compounds range from 140-522 mg/kg and hexavalent compounds range from 13-795 mg/kg (Government of Canada, 1994). Acute toxic effects in rats and mice exposed to high single doses of Cr(VI) include gastric ulcerations, pulmonary congestion, gastrointestinal oedema, diarrhoea and cyanosis (von Burg and Liu, 1993). 254. In rats, LC50 values for inhaled, highly soluble chromium hexavalent compounds are in the range of 33-65 mg/m 3 (von Burg and Liu, 1993). Associated effects include inflammatory responses and altered macrophage morphology. 255. Hexavalent chromium compounds can cause severe eye and skin irritation which can lead to ulceration. LD50 values for acute dermal exposure range from 400-677 mg/kg in rats. Associated effects include necrosis of the application site, diarrhoea, hypoactivity, dermal oedema and inflammation. 5.3.1.2 Human studies 256. Massive inhalations of chromium-containing fume can cause irritant damage to the upper and lower respiratory tracts. A study of ten volunteers exposed ‘briefly’ to CrO 3 reported nasal irritation above concentrations of 2.5 µg/m 3 (Kuperman, 1964). 89
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Department for Environment, Food an
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Department for Environment, Food an
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Contents Contents Terms of Referenc
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3.5 Justification for air quality g
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Terms of Reference The Expert Panel
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Dr Alison Searl BSc, MSc, PhD Insti
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Acknowledgments We thank the follow
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Expert Panel on Air Quality Standar
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Page 54 and 55: Expert Panel on Air Quality Standar
Page 99 and 100: Chapter 5 Chromium 5.1 Background 5
Page 101 and 102: Chromium stations, industry and for
Page 103: Chromium 245. Occupational exposure
Page 107 and 108: Chromium occasionally reached level
Page 109 and 110: Chromium 5.3.4.2 Human studies 272.
Page 111 and 112: Chromium 282. The WHO (2000) classi
Page 113 and 114: Chromium 5.5. Justification for air
Page 115 and 116: Chromium 5.6. Recommendation 304. 0
Page 117 and 118: Chromium HSE (2002). EH64 Summary C
Page 119 and 120: Chromium Nethercott, J., Paustenbac
Page 121 and 122: Chromium Von Burg, R. and Liu, D. (
Page 123 and 124: Abbreviations ACGIH American Confer
Page 125 and 126: Glossary Acute toxicity / effects A
Page 127 and 128: Glossary Epidemiology Epithelium Fe
Page 129 and 130: Glossary Metalloid Mucocilliary tra
Page 131 and 132: Glossary Threshold Limit Values (TL
Page 133 and 134: Appendix 1 Setting air quality stan
Page 135 and 136: Appendix 1 hours per week for a 40
Page 137 and 138: Appendix 1 arrive at a single conce
Page 139: ISBN 978-0-85521-185-1 £10.00 Prod
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