SILVER NANOTECHNOLOGIES AND THE ENVIRONMENT: OLD PROBLEMS OR NEW CHALLENGES?

Project on Emerging Nanotechnologies SILVER NANOTECHNOLOGIES AND THE ENVIRONMENT: OLD PROBLEMS OR NEW CHALLENGES? Samuel N. Luoma Project on Emerging Nanotechnologies is supported by THE PEW CHARITABLE TRUSTS PEN 15 SEPTEMBER 2008 TABLE OF CONTENTS 1 FOREWORD 4 ABOUT THE AUTHOR 5 EXECUTIVE SUMMARY 9 I. INTRODUCTION 14 II. FATE AND EFFECTS OF SILVER IN THE ENVIRONMENT 14 History of Silver Toxicity 14 Source-Pathway-Receptor-Impact 15 Sources: How Much Silver Is Released to the Environment by Human Activities? 18 Pathways: What Are the Concentrations of Silver in the Environment? 20 Pathways: Forms and Fate 22 Receptor: In What Forms Is Silver Bioavailable? 25 Impact: Toxicity of Silver 35 III. EMERGING TECHNOLOGIES AND NANOSIL ER 35 Conceptual Framework 35 Sources of Nanosilver and Potential Dispersal to the Environment 39 Mass Discharges to the Environment from New Technologies 44 Pathways of Nanosilver in the Environment 47 Is Nanosilver Bioavailable? 51 How Does Nanosilver Manifest Its Toxicity? 57 I . THE WAY FORWARD: CONCLUSIONS AND RECOMMENDATIONS SILVER NANOTECHNOLOGIES AND THE ENVIRONMENT: OLD PROBLEMS OR NEW CHALLENGES? Samuel N. Luoma PEN 15 SEPTEMBER 2008 The opinions expressed in this report are those of the author and do not necessarily reflect views of the oodrow Wilson International Center for Scholars or The Pew Charitable Trusts. FOREWORD Dr. Samuel Luoma has given us an excellent description and analysis of the science of silver and nanosilver. His paper raises many questions for policy makers. Its subtitle, “Old Problems or New Challenges,” is appropriate, because the subject of the paper is both. Metals are among the oldest of environmental problems. Lead, silver and mercury have posed health hazards for thou-sands of years, and they are as persistent in the environmental policy world as they are in the environment. Nanotechnology is a new challenge, but the scope of the policy issues it presents is as broad and difficult as the technology itself. As the paper makes clear, there is much we do not know about the environmental pathways of nanosilver, its environmental effects and its impact on human health. However, as Luoma notes, ionic silver, a form of nanosilver, when tested in the laboratory, is one of the most toxic metals to aquatic organisms. Ionic silver is being used now in washing machines and other products. The need for research is urgent. The major experiment being conducted now is to put nanosilver products on the market, expose large numbers of people and broad areas of the envi-ronment and then wait and hope that nothing bad happens. This is a dangerous way to pro-ceed. The experiments need to come before the marketing so that damage can be avoided rather than regretted. Dr. Luoma employs a useful environmental framework, starting with sources of nanosilver, then dealing with its pathways in the environment and ending with receptors and impact. Policy makers use the same model, only in reverse. They start with the question of whether there is an impact, then analyze the environmental pathways and finally deal with whether and how to control the sources. The impacts are the policy starting point, so the fact that less than 5 percent of the money being spent on nanotechnology by the U.S. government is being spent to study health and envi-ronmental impacts demonstrates a questionable sense of priorities. That is the major policy issue. However, there is also a need for surveillance and reporting. Workers, consumers, lakes and streams are being exposed to nanosilver and, while the experimentation is unfortunate, society should at least learn from it. People working with nano need to be monitored, and key aspects of the environment exposed to nanosilver should be investigated. Some of this will be done by scientific institutions, public and private. However, some of it, for example, medical monitoring of workers, may require government regulation. There is another connection between regulation and impacts, one that is less well recognized. As Luoma notes, “the formulation and form of a nanoparticle has great influence on the risks that it poses.” Silver in different nanoproducts can be in the form of silver ions, silver colloid solutions or silver nanoparticles. The nanosilver can come in different shapes, have different elec-trical charges and be combined with other materials and coated in different ways. Each of these factors, as well as others, affects toxicity and environmental behavior. If we are to discover how these different factors impact nanosilver’s toxicity and environmental behavior, it will only be by testing a large number of specific products that have different characteristics. This is not the kind 1 ... - tailieumienphi.vn