# Health Impact Assessment from Rice Straw Production in Cambodia
## 1 Introduction  
The Cambodia economy is heavily dependent on agriculture, and recent agricultural breakthroughs have helped many people escape poverty [1]. Cambodia is one of the ten countries of the Association of Southeast Asian Nations (ASEAN), having joined the organization on 30 April 1999. The total population of Cambodia was estimated at 15.55 million in 2019, with average annual growth of 1.4% [2]. Rice is the main food in Cambodia, with an estimated domestic consumption of 4.2 million tons in 2021 [3]. According to the annual report of the Ministry of Agriculture, Forestry, and Fisheries (Cambodia), the total rice production in the country in 2021 was estimated as more than 12 million tons from a total farmed area of 3,497,682 hectares [4]. It is Cambodia's most important agricultural export product, the primary source of crop value-added products, and the main driver of agricultural growth, with rice cultivation covering more than 80% of all farmed area in the country [5]. Haze is an airborne mixture containing enough smoke, dust, moisture, and vapor to reduce visibility and is characterized by a high concentration of particulate matter mainly made of fine particulate matter less than 10 mm, which is produced by large-scale forest and land fires [6]. Over the past two decades, there have been experiences of transboundary haze pollution caused by forest and land fires in the ASEAN countries [7]. Due to the air pollution from forest fires and land fires, ASEAN members including Cambodia have agreed and created the roadmap for ASEAN cooperation towards Transboundary haze pollution control (Haze-Free ASEAN by 2020) by focusing on indicators PM\({}_{2.5}\) and PM\({}_{10}\)[7]. Cambodia, a country in Indochina, is one of the world's most active fire hotspots. This is a matter of serious concern due to the high population density being close to high-frequency fire zones [8]. The open burning of agricultural residue in Southeast Asia (SEA) accounts for 43% of the global total of open biomass burning (BB), which substantially contributes to air pollution [9; 10]. Among the BB categories, agricultural residue contributes 23% of the worldwide biomass burning total [11]. Biomass burning is a source of global air pollution, which commonly contains primary particulate matter (PM\({}_{2.5}\) and PM\({}_{10}\)) and secondary formations of NH\({}_{3}\), NO\({}_{\times}\), and SO\({}_{2}\)[12]. In Cambodia and other ASEAN countries, during the dry season, the open burning of rice straw after harvest is common-a practice that may greatly increase ambient air pollution [13]. Diverse farming practices such as the open burning of residue biomass, combustion of diesel or gasoline, and the use of fertilizers, extending all the way from large, sensitive, and specialist commercial operations to subsistence-level cultivation, all result in PM\({}_{2.5}\) formation. The rice cultivation activities that generate pollutants such as sulfur oxide (SO\({}_{\times}\)), nitrogen oxide (NO\({}_{x}\)), and ammonia (NH\({}_{3}\)) play a key role in PM\({}_{2.5}\) formation. PM\({}_{2.5}\) is an aerodynamic particle with a diameter equal to or less than 2.5 um, which impacts air quality, causes air pollution, and impacts human health [14]. Furthermore, Southeast Asia's air pollution is strongly affected by biomass burning at all scales, from regional to local [15]. Ambient fine particulate matter (PM\({}_{2.5}\)) is a key risk factor for health impacts and is likely to be harmful to humans, with extensive and well-documented concerns about disease reported in the literature [16]. Globally, 4.1% of deaths are attributed to indoor air pollution [17]. A WHO report on the impact of air pollution stated that the premature deaths of 2.2 million people every year are linked to air pollution in the home and outdoors. Among these causes of death are pneumonia (8%), ischemic heart disease (29%), stroke (27%), chronic obstructive pulmonary disease (22%), and lung cancer (14%) [18]. In Cambodia, rice straw is widely available and low in value.