Through quantifying the costs of not acting on air pollution, this assessment aims to increase the evidence base to support policymakers and decision makers in Cambodia to take further action and prioritize ambitious policies and cost-effective measures to improve air quality. It provides an initial quantification of some of the costs of inaction from tackling air pollution in Cambodia, through quantifying and costing the health benefits which could be achieved from implementing 12 specific mitigation solutions. It also highlights some other benefits, such as for climate change, which could be achieved if these solutions are implemented.