While in the beginning of the environmental debate, conflicts over environmental and technological issues had primarily been understood in terms of ''risk'', over the past two decades the relevance of ignorance, or nonknowledge, was emphasized. Referring to this shift of attention to nonknowledge the article presents two main findings: first, that in debates on what is not known and how to appraise it different and partly conflicting epistemic cultures of nonknowledge can be discerned and, second, that drawing attention to nonknowledge in technology conflicts results in significant

How can and how should our societies deal with potential-and possibly not even fully known and foreseeable-risks posed by innovations and new products in areas such as nanotechnology, agro-biotechnology, or chemistry? The editorial team of the European Environment Agency (EEA) report Late Lessons from Early Warnings gives a rather unusual advice: "Acknowledge and respond to ignorance, as well as uncertainty and risk, in technology appraisal and public policy making" (EEA 2001, p. 168). This recommendation is based on the analysis of fourteen cases of delayed recognition of environmental and health risks, amongst them chlorofluorocarbons (CFC)-which contribute to the ozone hole-, asbestos, and mad cow disease (BSE). Considering these and other examples, we argue that environmental politics and research should take into account not only known and (more or less) well-defined risks and uncertainties, but also completely unknown, unanticipated and for a long time unrecognised effects. This corresponds with new insights from science and technology studies showing that the sciences do not only generate knowledge but also increase ignorance concerning the possible side effects of scientific innovations and their technological application (Ravetz 1986, Funtowicz and Ravetz 2001, Wynne 1992, Nowotny et al. 2001). 1 In order to clarify that such non-knowl-Scientific Cultures of Non-Knowledge in the Controversy over Genetically Modified Organisms (GMO) The Cases of Molecular Biology and Ecology

The concept of epistemic cultures and their strategies of evidence-making should be investigated more explicitly with respect to other risk policy fields The analysis of hybrid regimes of knowledge should be deepened by looking at the complex interactions between institutional, discursive and practical rules affecting risk assessment.

We review here the concept of sustainable chemistry (SC), which is still in its early development.