The toxic legacy of the worst flood in Thai history will remain long after the waters have receded.This year's unusually long rainy season has left many parts of Thailand, Laos and Cambodia inundated and has resulted in the worst flooding crisis in Thailand, in the last 50 years. Provinces in the Central Plains and many districts in the north, east and west of Bangkok are now under water. The huge volume of water is such that flood levels are three metres deep in some areas.
So far, the death toll in Thailand has surpassed 500.
At least seven major industrial parks in Ayutthaya and Pathum Thani have been submerged. Two major eastern industrial estates _ Lat Krabang and Bang Chan _ 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 flood-damaged industrial estates and other infrastructure, the environmental pollution has been largely overlooked.
Deluge water is not only floodwater. Indeed, significant amounts of industrial waste, hazardous substances, raw sewage and 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 floodwaters 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 absorbed by soil particles and trapped in pore spaces within the soil matrix itself. Exposure to these contaminated soils and groundwater 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 hazard to human health.
Inundated buildings also provide a breeding ground for harmful moulds and fungi. Moulds are ubiquitous in the biosphere but when mould spores are present in abnormally high quantities, they can pose a threat to humans by causing allergic reactions, asthma episodes, fungal infections such as mycosis, irritations of the eyes, nose and throat, sinus congestion and other respiratory problems. Moulds excrete toxic compounds called mycotoxins under certain environmental conditions and some mycotoxins can be harmful, even lethal, to humans with high dosage exposure. It is important that buildings that have been inundated are inspected by a specialist for the presence of potentially harmful moulds and fungi once the waters have subsided.
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 finalising 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 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.
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 abated. 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.
PHOTO: THITI WANNAMONTHA