What is considered a “safe dose” is a complicated concept that depends on several factors besides scientific evidence (toxicity): for example, economic factors (cost of eliminating or reducing the exposure), public health factors (total disease burden of a community), and social and political factors (what the general public and politicians consider acceptable).

In general, for cancer-causing substances there is no established “safe dose” and a policy based on 100% avoidance is advisable, for example, for some work-related cancer-causing substances such as asbestos; however, this is not possible for many environmental chemical substances, such as some air pollutants. For instance, the European Union bans all types of utilization of asbestos as a way to eliminate exposure. However, some exposures are so low that they are currently considered acceptable by society: for example, for the protection of human health the European Union has established two limit values for particulate matter (PM10), a component of air pollution: the PM10 daily mean value and the PM10 annual mean value (Air Quality Directive 2008/EC/50).