challenges wide scale support for PES and its implementation. Air pollution The World Bank estimates that deaths in Thailand attributable to air pollution have risen from 31,000 in 1990 to roughly 49,000 in 2013. Industrial growth has created high levels of air pollution in Thailand. Vehicles and factories contribute to air pollution, particularly in Bangkok, which experienced high levels of air pollution in the winter of 2019. Recent research (2019) points to agricultural burning as the root cause of PM 2.5 pollution in Thailand. PM 2.5 is a measurement of particulates in the atmosphere smaller than 2.5 microns. The Bangkok metropolitan region, which consists of the Bangkok Metropolitan Administration (BMA) and the four surrounding provinces (Nonthaburi, Pathum Thani, Nakhon Pathom, and Samut Prakan), holds about 20% of the national population and over half of the country's factories. Due to a lack of treatment facilities, increasing volumes of hazardous substances generated by industrial activities have caused serious dumping issues. Unless treatment facilities are built and institutions starts to regulate strictly, environmental contamination caused by hazardous waste threatens to become Thailand's worst environmental problem in the future. Thailand's Pollution Control Department (PCD) and other agencies have developed standards in order to reduce air pollution. The standards focus on shifting to lower-emissions vehicle engines and improving public transportation. In 1999, 80% of the motorcycles on the road in Bangkok had environmentally unfriendly two-stroke engines. Diesel trucks and buses also contribute many pollutants. In most areas of the country, air pollutants for vehicles are now within acceptable levels according to national standards. Factories and power plants have been required to reduce emissions. In 2002, Bangkok and the rest of the central region contributed between 60 and 70% of the country's industrial emissions. Most power plants rely on burning fossil fuels. Other sources of air pollution include garbage burning, open cooking, and agricultural burning practices, including deliberate forest fires. Agricultural burning in Southeast Asia often creates haze. In 2003 Thailand ratified the ASEAN Agreement on Transboundary Haze Pollution to reduce the haze from forest fires, but issues throughout the region are still common. Wildfires are started by local farmers during the dry season in northern Thailand for a variety of purposes, with February and March as the two months when conditions are at their worst. In research conducted between 2005 and 2009 in Chiang Mai, average PM10 rates during these months were found to be