SLP Environmental Co., Ltd - An ASEAN Environmental Consultancy

The toxic legacy of Thailand’s ‘Great Flood’ will remain long after the waters have receded


This year’s unusually long rainy season has left many part of Thailand, Lao and Cambodia inundated and resulted in the worst flooding crisis in Thailand for at least 50 years. The provinces of the central plains and many districts in the north, east and west of metropolitan Bangkok are now effectively under water. The huge volume of floodwater is such that flood levels are 3 metres deep in some areas and they are not expected to recede for several weeks as the natural and manmade drainage systems simply cannot cope with the deluge.

Towns, villages, historic temples, paddy fields, industrial estates, factories, landfills, water treatment plants, airports and other critical infrastructure have all been inundated and the social and economic costs of the disaster will be daunting. At the time of writing at least 380 people have been killed in Thailand alone and another 250 in neighbouring Cambodia and rescue workers are scrambling to prevent a humanitarian disaster

According to the Labour Ministry, at least seven major industrial parks have been flooded and over 10,800 factories, in 28 provinces have been forced to close, affecting over 447,000 workers. Thailand has become a global hub for car and electronic components manufacturing and not only have Honda and Toyota been forced to stop all production in Thailand but the global supply chain for many other critical electronic components has also been severely disrupted which has adversely affected tens of thousands of other businesses.

In Ayutthaya and Bang Pa-In the Hi-Tech and Rojana Industrial Estates have been inundated. The most recent industrial estate to be evacuated was Nava Nakorn in Pathum Thani (Thailand’s oldest industrial estate) which houses 227 factories and employs over 170,000 workers. Companies with operations there include Canon, Nikon, Nestle, Toshiba, Casio, Seiko and hard drive manufacturer Western Digital, which had already had to shut down production at another industrial estate. Now in the east of Bangkok, the Lat Krabang and Bang Chan Industrial Estates have been heavily reinforced with sandbags to protect the facilities and infrastructure therein.

While the government deals with the immediate crisis and puts in place plans for the eventual rehabilitation of the food damaged industrial estates, manufacturing sector and other infrastructure, the environmental pollution legacy of the floods has been largely overlooked. Significant amounts of industrial waste, hazardous substances, raw sewage and other miscellaneous toxic chemicals have been released into the environment as a result of the flooding and these will have an immediate negative impact on water quality and human health. The floods will also have a toxic legacy in the form of soil, sediment and groundwater contamination which will continue to represent a risk to human health and the environment long after the flood waters have receded.

Groundwater resources may be contaminated by toxic chemicals and harmful pathogens such as faecal coliforms and E-Coli that can enter aquifers directly via groundwater abstraction wells and indirectly via downward percolation of contaminated waters through the soil profile. Toxic chemicals and harmful pathogens may also be sorbed to soil particles and trapped in pore spaces within the soil matrix itself. Exposure to these contaminated soils and groundwaters can represent a serious risk to the health of exposed individuals.

Contaminants can also leach out of river sediments and be transferred up the food chain via the aquatic ecosystem. Consumption of affected species such as freshwater shrimp and fish represents a potential risk to human health.

Inundated buildings also provide a breeding ground for harmful molds and fungi. Molds are ubiquitous in the biosphere but when mold spores are present in abnormally high quantities, they can present a health hazard to humans by causing allergic reactions, asthma episodes, fungal infections (mycosis), irritations of the eye, nose and throat, sinus congestion and other respiratory problems. Molds excrete toxic compounds called mycotoxins under certain environmental conditions and certain mycotoxins can be harmful, or even lethal, to humans when exposure is high enough. It is important that buildings that have been inundated are inspected by a specialist for the presence of potentially harmful molds and fungi once the waters have receded.

The toxic legacy of the floods may also have financial implications for the owners and occupiers of affected properties such as industrial units when they come to divest of the property or hand back their lease. It is common practice for potential purchasers to conduct environmental due diligence (EDD) to determine the contamination status of the property before finalizing any transaction, this is often referred to as an Environmental Baseline Study (EBS). Furthermore, land owners may require lessees to conduct an EBS before they hand back the property to demonstrate that their operations and activities have not resulted in soil or groundwater contamination. These studies are an integral component of the risk and liability management process that accompanies most significant business transactions.

It is common to collect soil and groundwater samples during these studies and submit them for laboratory analysis for a range of common contaminants. If contamination is found during this stage of the transaction process it can have significant financial and legal implications for the property owner or lessee.

One way to avoid the potential for this situation to arise in the future is to commission a soil and groundwater sampling and testing study as soon as the floodwaters have receded. If contamination is present as a direct result of the floods then the property owner or lessee may be able to claim the costs associated with assessing and cleaning up the contamination from their insurer.


Customer comments

  1. By Michael Roland on

    Mold proliferates in that environment. I produced and directed the feature-length documentary Black Mold Exposure at, and I can assure you that mold is not something to take lightly.