Background. Environmental pollution has become the leading risk factor for death in low- and middle-income countries (LMICs). The World Health Organization and others calculate that exposures to polluted air - indoor and outdoor, water and soil resulted in 8.4 million deaths in LMICs in 2012. By comparison, HIV/AIDS causes 1.5 million deaths per year, and malaria and tuberculosis Less than 1 million each. The diseases caused by pollution include the traditional scourges of pneumonia and diarrhea, but increasingly they also include chronic, non-communicable diseases (NCDs) such as such as heart disease, stroke and cancer. Method. We review the diseases caused by pollution and the multiple economic and human burdens that these diseases impose on health systems in countries with already limited resources. Results. We find that diseases caused by pollution increase health care costs, especially for high-cost NCDs. They impose an unnecessary load on health care delivery systems by increasing hospital staffing needs and thus diverting resources from essential prevention programmes such as childhood immunizations, infection control and maternal and child health. They undermine the development of poor countries by reducing the health, intelligence and economic productivity of entire generations. Pollution is highly preventable and pollution prevention is highly cost-effective. Yet despite their high economic and human costs and amenability to prevention, the diseases caused by pollution have not received the attention that they deserve in policy planning or in the international development agenda. Conclusion. Pollution is not inevitable. It is a problem that can be solved in our lifetime. Given the great impact of pollution on health and health care resources and the high cost-benefit ratio of pollution prevention, efforts to mitigate pollution should become a key strategic priority for international funders and for governments of LMICs. Recommendation. Assisting LMICs to prioritize disease prevention through the management of pollution is a highly cost-effective strategy for enhancing population health, reducing the burden on limited health resources and advancing national development.