Rockström et al. (2009a, 2009b) have warned that humanity must reduce anthropogenic impacts defined by nine planetary boundaries if "unacceptable global change" is to be avoided. Chemical pollution was identified as one of those boundaries for which continued impacts could erode the resilience of ecosystems and humanity. The central concept of the planetary boundary (or boundaries) for chemical pollution (PBCP or PBCPs) is that the Earth has a finite assimilative capacity for chemical pollution, which includes persistent, as well as readily degradable chemicals released at local to regional scales, which in aggregate threaten ecosystem and human viability. The PBCP allows humanity to explicitly address the increasingly global aspects of chemical pollution throughout a chemical's life cycle and the need for a global response of internationally coordinated control measures. We submit that sufficient evidence shows stresses on ecosystem and human health at local to global scales, suggesting that conditions are transgressing the safe operating space delimited by a PBCP. As such, current local to global pollution control measures are insufficient. However, while the PBCP is an important conceptual step forward, at this point single or multiple PBCPs are challenging to operationalize due to the extremely large number of commercial chemicals or mixtures of chemicals that cause myriad adverse effects to innumerable species and ecosystems, and the complex linkages between emissions, environmental concentrations, exposures and adverse effects. As well, the normative nature of a PBCP presents challenges of negotiating pollution limits amongst societal groups with differing viewpoints. Thus, a combination of approaches is recommended as follows: develop indicators of chemical pollution, for both control and response variables, that will aid in quantifying a PBCP(s) and gauging progress towards reducing chemical pollution; develop new technologies and technical and social approaches to mitigate global chemical pollution that emphasize a preventative approach; coordinate pollution control and sustainability efforts; and facilitate implementation of multiple (and potentially decentralized) control efforts involving scientists, civil society, government, non-governmental organizations and international bodies.

Department of Biological and Environmental Sciences University of Gothenburg Box 100 SE 405 30 Gothenburg Sweden

Department of Earth and Environmental Sciences University of Milano Bicocca Piazza della Scienza 1 Milan 20126 Italy

Department of Earth Sciences University of Toronto 22 Russell Street Toronto M5S 3B1 Ontario Canada

Department of Environmental Science and Analytical Chemistry Stockholm University SE 106 91 Stockholm Sweden

Department of Management Engineering Technical University of Denmark Nils Koppels Allé Building 426 D DK 2800 Kgs Lyngby Denmark

Environmental Systems Analysis Department of Energy and Environment Chalmers University of Technology SE 412 96 Gothenburg Sweden

Forschungsstelle für Atmosphärische Chemie Dr Hans Frisch Str 1 3 Universität Bayreuth D 954 48 Bayreuth Germany

Graduate School of Oceanography University of Rhode Island South Ferry Road Narragansett RI 02882 United States

Institute for Chemical and Bioengineering ETH Zürich Wolfgang Pauli Str 10 8093 Zürich Switzerland

Leuphana University Lüneburg D 21335 Lüneburg Germany

Research Centre for Toxic Compounds in the Environment Faculty of Science Masaryk University Kamenice 753 5 625 00 Brno Czech Republic

Stockholm Environment Institute Linnégatan 87D Box 24218 Stockholm Sweden

Strategic Risk Management Research Section Center for Environmental Risk Research National Institute for Environmental Studies 16 2 Onogawa Tsukuba Ibaraki 305 8506 Japan

Swedish Toxicology Sciences Research Center Forskargatan 20 Sweden

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