Asbestos in Drinking-water Background document for development of WHO Guidelines for Drinking-water Quality 14 December 2020 Version for public review © World Health Organization 202X Preface To be completed by WHO Secretariat Acknowledgements To be completed by WHO Secretariat Abbreviations used in the text A/C Asbestos-cement ATSDR Agency for Toxic Substances and Disease Registry (USA) CHO Chinese hamster ovary FT-IR Fourier-transform infrared spectroscopy GI Gastrointestinal LECR Lifetime excess cancer risk MFL Million Fibres per Litre PCM Phase contrast microscopy SHE Syrian hamster embryo SIR Standardised incidence ratio F-yr/mL Total number of fibres in one year per mL of air (More potential abbreviations) CI Confidence interval NTU Nephelometric turbidity units TEM Transmission electron microscopy SAED Selected-area electron diffraction ROS Reactive oxygen species Table of Contents 1.0 EXECUTIVE SUMMARY ..................................................................................................................................... 1 2.0 GENERAL DESCRIPTION .................................................................................................................................... 1 2.1 Identity ................................................................................................................................................................. 1 2.2 Physicochemical properties ................................................................................................................................. 1 2.3 Organoleptic properties ....................................................................................................................................... 1 2.4 Major uses and sources ........................................................................................................................................ 1 2.5 Environmental fate ............................................................................................................................................... 2 3.0 ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE ................................................................................ 2 3.1 Water ................................................................................................................................................................... 2 3.1.1 General drinking water ................................................................................................................................. 2 3.1.2 A/C pipe contact with drinking water ........................................................................................................... 3 3.2 Food ..................................................................................................................................................................... 4 3.3 Air ........................................................................................................................................................................ 4 3.4 Bioaccumulation .................................................................................................................................................. 5 3.5 Estimated total exposure and relative contribution of drinking-water .................................................................. 5 4.0 TOXICOKINETICS AND METABOLISM IN HUMANS AND LABORATORY ANIMALS ........................... 6 4.1 Absorption ........................................................................................................................................................... 6 4.2 Distribution .......................................................................................................................................................... 7 4.3 Metabolism .......................................................................................................................................................... 7 4.4 Excretion .............................................................................................................................................................. 7 5.0 EFFECTS ON HUMANS........................................................................................................................................ 7 5.1 Acute exposure .................................................................................................................................................... 8 5.2 Short-term exposure............................................................................................................................................. 8 5.3 Long-term exposure ............................................................................................................................................. 8 5.3.1 Systemic effects ............................................................................................................................................ 8 5.3.2 Neurological effects ...................................................................................................................................... 8 5.3.3 Reproductive and developmental effects ...................................................................................................... 8 5.3.4 Immunological effects .................................................................................................................................. 8 5.3.5 Genotoxicity and carcinogenicity ................................................................................................................. 8 6.0 EFFECTS ON ANIMALS AND IN VITRO TEST SYSTEMS ............................................................................. 11 6.1 Acute exposure .................................................................................................................................................. 11 6.2 Short-term exposure........................................................................................................................................... 11 6.3 Long-term exposure ........................................................................................................................................... 12 6.3.1 Systemic effects .......................................................................................................................................... 12 6.3.2 Neurological effects .................................................................................................................................... 12 6.3.3 Reproductive and developmental effects .................................................................................................... 12 6.3.4 Immunological effects ................................................................................................................................ 12 6.3.5 Genotoxicity and carcinogenicity ............................................................................................................... 12 6.5 Mode of action ................................................................................................................................................... 14 7.0 SUMMARY OF HEALTH EFFECTS .................................................................................................................. 14 8.0 PRACTICAL CONSIDERATIONS ...................................................................................................................... 14 8.1 Analytical methods and achievability ................................................................................................................ 14 8.2 Source control .................................................................................................................................................... 15 8.4 Treatment methods and performance ................................................................................................................. 16 9.0 CONCLUSIONS ................................................................................................................................................... 16 10.0 APPENDICES ..................................................................................................................................................... 17 10.1 REFERENCES ................................................................................................................................................ 17 ASBESTOS IN DRINKING-WATER DRAFT Background document for the WHO GDWQ, December 2020 1 1.0 EXECUTIVE SUMMARY 2 To be completed by WHO Secretariat 3 4 5 2.0 GENERAL DESCRIPTION 6 2.1 Identity 7 Asbestos is a general term for a group of naturally occurring fibrous silicate minerals containing iron, 8 magnesium, calcium, sodium, titanium, manganese, and combinations thereof. These minerals are divided 9 into two groups, namely serpentine (i.e. chrysotile, characterised by generally curly fibres) and amphibole 10 (i.e. amosite , crocidolite, anthophyllite, actinolite and tremolite), characterised by generally straight fibres) 11 (Klein et al., 1993; IARC, 2012; WHO, 2014). 12 2.2 Physicochemical properties 13 Asbestos minerals are polyfilamentous bundles comprised of long, flexible fibres of small diameter 14 (≤ 3 µm), which are easily separated (IARC, 2012). These fibres are thought of as chemically inert as they 15 do not evaporate, burn, dissolve or react with most chemicals. Chrysotile is easily degraded by strong acids, 16 whereas amphiboles are more resistant. The various forms of asbestos are generally resistant