This study provides an economic assessment of the health effects due to exposure to particulate matter PM_2.5 in three medium-size cities of northwestern Mexico: Los Mochis, Culiacan and Mazatlán. People in these cities are exposed to high pollutant concentrations that exceed limits suggested in domestic and international guidelines. PM_2.5 is an air contaminant negatively associated with people’s health when is highly concentrated in the atmosphere; its diameter is below 2.5 µm and causes the air to appear hazy when levels are elevated. To account for the economic impact of air pollution, a Health Impact Assessment (HIA) was used by the means of the European Aphekom Project. We figured the cost-savings of complying with current environmental standards and computed gains in life expectancy, total avoidable premature mortality, preventable cardiovascular disease, and the economic costs of air pollution related to PM_2.5. A formal analysis of air pollution epidemiology is not pursued in this paper. The cost of reducing PM_2.5 pollution associated with negative health outcomes was based on two different scenarios: Official Mexican Standard (NOM, Spanish acronym) and World Health Organization (WHO) environmental standards. The mean PM_2.5 concentrations in 2017 were 22.8, 22.4 and 14.1 µg/m³ for Los Mochis, Mazatlán and Culiacan, respectively. The mean avoidable mortality for all causes associated to PM_2.5 exposure in these cities was 638 for the NOM scenario (i.e., with a reduction to 12 µg/m³) compared to 739 for the WHO scenario (reduction to 10 µg/m³). Complying with the WHO guideline of 10 µg/m³ in annual PM_2.5 mean would add up to 15 months of life expectancy at age 30, depending on the city. The mean economic cost per year of the PM_2.5 effects on human life in these three cities was USD 600 million (NOM scenario) and USD 695 million (WHO scenario). Thus, effective public health and industrial policy interventions to improve air quality are socially advantageous and cost-saving to promote better health.