Cultivating a demand for clean cookstoves more

In their policy forum “a major environmental cause of death” (14 October, p. 180), W. J. Martin II and colleagues highlight the need to stimulate market demand for clean cookstoves because “a stove purchased by the consumer is inherently more valued than one that is received without charge.” This widely held view has been challenged, however, by evidence from recent randomized controlled trials studying other preventative health products.