The context of our study is Cambodia, a country with a tropical monsoon climate encompassing distinct wet and dry seasons and a high incidence of floods and droughts. In Cambodia, national-level climate change models predict a considerable increase in mean annual temperature, ranging between 0.7° and 2.7° by 2060 and 1.4° and 4.3° by 2100. Mean annual rainfall is expected to rise, particularly during the wet season (Thoeun, 2015). The associated extreme weather is likely to influence the prevalence and transmission of various diseases, particularly water-borne illnesses<sup>2</sup> like diarrhea (Davies et al., 2014). We study how weather shocks impact diarrhea incidence in this paper. Although Cambodia’s share of global greenhouse gas (GHG) emissions was only 0.14 percent in 2019, they grew at an average annual rate of 8 percent from 2010 to 2019 (World Bank, 2023b). The country’s rapid industrialization and urbanization have increased emissions and the other face of the same coin, air pollution levels, creating a pressing need to investigate the relationship between pollution and health outcomes.<sup>3</sup> In what follows, we choose air pollution’s impact on cough in children since lower respiratory infections are the second cause of death in Cambodia (IHME, 2023). Studying the link between climate change and health is even more important in Cambodia, where increased morbidity is likely to have significant consequences on households’ finances, particularly for the poorest. Indeed, out-of-pocket expenditure represents 60.6% of current health expenditure (WHO, 2023; World Bank, 2024).

This study leverages high-resolution satellite data measuring environmental hazards, as well as geo-referenced individual-level indicators from the Demographic and Health Surveys. We use flexible binned specifications that simultaneously consider the impact of temperature, precipitation, and air pollution. The latter is a crucial dimension of environmental degradation and one of the negative consequences of transport and industrial emissions. We also assess the effectiveness of adaptation actions for children’s diarrhea incidence by studying their effectiveness in mitigating the adverse effect of weather on diarrheal diseases. Finally, we employ climate simulations to project the incidence of child diarrhea in Cambodia under different climate and development scenarios. We consider two extreme climate scenarios, also called Shared Socioeconomic Pathways (SSPs): SSP1.19, characterized by very low greenhouse gas emissions, and SSP3.70, marked by high emissions. Combining our estimates of the impact of weather and toilet ownership on diarrhea incidence with the IPCC climate scenarios, we forecast the effectiveness of different toilet ownership scenarios in reducing the

> 2There are several water-related diseases with a moderate-to-high incidence in Cambodia: diarrheal diseases, typhoid fever, leptospirosis, melioidosis, viral hepatitis, and schistosomiasis (McIver et al., 2016a).

> 3The share of people in urban areas in Cambodia has grown steadily since the 1980s. In 2022, the percentage of people living in urban areas was 25.1% in Cambodia; it was only 10% in 1980 (World Bank, 2023a).

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