Carbon nanotubes Types, products, market, and provi- sional assessment of the associated risks to man and the environment Environmental project No. 1805, 2015 Title: Authors: Carbon nanotubes Keld Alstrup Jensen, Senior Researcher1 Jesper Bøgelund, Senior Consultant2 Petra Jackson, Researcher1 Nicklas Raun Jacobsen, Senior Researcher1 Renie Birkedal, Researcher1 Per Axel Clausen, Senior Researcher1 Anne Thoustrup Saber, Senior Researcher1 Håkan Wallin, Professor1 Ulla Birgitte Vogel, Professor1 1 Danish NanoSafety Centre National Research Centre for the Working Environment, Lersø Parkallé 105, DK-2100 Copenhagen, DENMARK 2 Danish Technological Institute Gregersensvej 1, 2630 Taastrup, DENMARK DK2100 Copenhagen Published by: The Danish Environmental Protection Agency Strandgade 29 DK-1401 Copenhagen K www.mst.dk Year: ISBN no. 2015 978-87-93352-98-8 Disclaimer: The Danish Environmental Protection Agency publishes reports and papers about research and development projects within the environmental sector, financed by the Agency. The contents of this publication do not necessarily represent the official views of the Danish Environmental Protection Agency. By publishing this report, the Danish Environmental Protection Agency expresses that the content represents an important contribution to the related discourse on Danish environmental policy. Sources must be acknowledged. 2 Carbon nanotubes Contents Contents .................................................................................................................... 3 Preface ...................................................................................................................... 6 Summary and conclusion .......................................................................................... 7 Sammenfatning og konklusion ................................................................................ 16 1. Introduction ..................................................................................................... 25 2. Types and characteristics of carbon nanotubes ................................................. 28 2.1 Summary ........................................................................................................................... 28 2.2 Morphological and structural types of carbon nanotubes .............................................. 30 2.2.1 Bonding of carbon ............................................................................................................. 34 2.2.2 Types and roles of structural defects ................................................................................ 35 2.3 Synthesis Methods ............................................................................................................ 37 2.3.1 Chemical Vapor Deposition .............................................................................................. 38 2.3.2 Carbon arc discharge ........................................................................................................ 42 2.3.3 Laser Ablation ................................................................................................................... 42 2.4 Chemical and Structural Purification .............................................................................. 43 2.5 Functionalization .............................................................................................................. 50 2.6 Types and characteristics of commercial CNT ................................................................. 51 2.6.1 SWCNT ............................................................................................................................... 51 2.6.2 DWCNT ............................................................................................................................. 53 2.6.3 MWCNT............................................................................................................................. 53 2.6.4 Other CNT structures........................................................................................................ 55 2.7 Concluding remarks .......................................................................................................... 55 3. Main current and near-future applications of CNT ............................................ 57 3.1 Summary ........................................................................................................................... 57 3.2 Global CNT production volume and application areas ................................................... 58 3.3 Global market value and production volume .................................................................. 58 3.3.1 Global product trade value and main industrial sectors ................................................. 59 3.4 Examples of CNT-based products in specific application areas ......................................61 3.4.1 Electronics ......................................................................................................................... 62 3.4.2 Coatings ............................................................................................................................. 63 3.4.3 Energy................................................................................................................................ 65 3.4.4 Materials ............................................................................................................................ 65 Carbon nanotubes 3 3.4.5 Biomedical ......................................................................................................................... 70 3.5 Concluding remarks ........................................................................................................... 71 4. Exposure to man and the environment ............................................................. 72 4.1 Summary ........................................................................................................................... 72 4.2 Exposure and environmental release of CNT .................................................................. 73 4.2.1 Exposure and release during synthesis and product manufacturing ............................. 74 4.2.2 Exposure and release during consumer use and disposal ............................................... 81 4.3 Concluding remarks .......................................................................................................... 85 5. Human health effects of carbon nanotubes ....................................................... 87 5.1 Summary ........................................................................................................................... 87 5.2 Biodistribution .................................................................................................................. 88 5.2.1 Inhalation .......................................................................................................................... 88 5.2.2 Oral exposure to CNT ....................................................................................................... 90 5.2.3 Biological distribution from blood. .................................................................................. 90 5.2.4 Biological distribution following peritoneal deposition. ................................................. 93 5.2.5 Biodistribution summary ................................................................................................. 94 5.3 Toxicological effects of pulmonary exposure to CNT ...................................................... 95 5.3.1 Instillation of SWCNT ...................................................................................................... 95 5.3.2 Inhalation and aspiration exposure to SWCNT ............................................................... 95 5.3.3 Instillation of MWCNT ..................................................................................................... 96 5.3.4 Aspiration of MWCNT ...................................................................................................... 96 5.3.5 Inhalation exposure to MWCNT ...................................................................................... 96 5.3.6 Studies performed according to OECD guidelines .......................................................... 96 5.4 Genotoxicity and Cancer ................................................................................................... 97 5.5 Cardiovascular effects of CNT .......................................................................................... 99 5.5.1 Pulmonary exposure to CNT ............................................................................................ 99 5.5.2 Systemic administration of CNT ...................................................................................... 99 5.6 Immunotoxic effects of CNT ............................................................................................. 99 5.7 Reprotoxicological effects ............................................................................................... 100 5.8 Dermal toxicity of CNT ................................................................................................... 100 5.9 Concluding remarks ......................................................................................................... 101 6. Ecotoxicology ................................................................................................. 104 6.1 Summary ........................................................................................................................