Studies support probable long-term safety of MRI.

30 JULY 2010 VOL 329 SCIENCE www.sciencemag.org Sustainability: A Household Word I THANK Q. WANG AND G. P. PETERS ET AL. (“China’s environmental civilian activism” and “Effects of China’s economic growth,” Letters, 14 May, p. 824) for responding to my Policy Forum, “China’s road to sustainability” (2 April, p. 50). Their Letters reiterated important forces affecting sustainability, which I have previously addressed (1–3). In contrast to Peters et al., I maintain that the direct and indirect impacts of households on the environment (4) are important and deserve much more attention. For example, the household sector is the major direct and indirect consumer of energy (5). From 1980 to 2006, direct residential electricity usage in China increased 31-fold, whereas electricity usage in other sectors increased only 8-fold (6). In 2005, households’ indirect energy usage (e.g., energy usage by other sectors that produce and transport products for households) was 4.5 times as high as their direct energy usage; between 1992 and 2005, indirect energy usage increased 6.3 times as fast as direct energy usage (7). CO 2 emissions from households increased over time (5, 8). With increasing domestic demand and household proliferation (rapid increase in the number of households) in China, household impacts on the environment may continue to rise in the future. I agree with Wang that more people in China have been involved in environmental civilian activism against environmental damage from industries, but it is essential to consider their own increasing environmental impacts that result from lifestyle changes such as increasing consumption, increasing demand for household products, and increasing divorces (9). To minimize the environmental impacts of industries, it is important to reduce household demand for industrial products. JIANGUO LIU Center for Systems Integration and Sustainability, Michigan State University, East Lansing, MI 48823, USA. E-mail: [email protected]