Most developing countries are just beginning to take environmental protection seriously. In some cases it is common to copy regulations from developed countries; however, determining how much protection is required is difficult, ideally requiring that the costs and risks be considered to propose a realistic and effective policy. Chile has serious problems with arsenic pollution associated to emissions from its copper smelters. To regulate these emissions, a strict ambient concentration standard, applicable to the whole country, is being proposed that reduces risks to an acceptable level. However, little is known about the exposure and health effects associated to current emission levels, and the corresponding costs of reducing emissions. The results of a three-year project that combines engineering, economics and health information sheds light on these costs and risks for different values of ambient standards. These show that there are 'win-win' options that obtain significant health improvements at low, even negative, costs. However, costs quickly increase as the concentration standard becomes more stringent, with few additional health benefits. In many locations naturally high background levels of arsenic make it very costly or even impossible to reach the desired goal. These results make it necessary to examine the use of a case-by-case regulation for each source, rather than a general one based on a unique ambient quality goal. They also suggest that copying standards or risk criteria used in developed contexts can be extremely expensive.