When I first found out I would be spending my summer researching arsenic contamination in Thailand, I couldn’t help but think of the 1940’s classic film, “Arsenic and Old Lace,” which was my first introduction to arsenic and its poisonous characteristics. In the dark comedy, Cary Grant’s character discovers his two sweet elderly aunts are actually serial killers that poison unsuspecting lonely old men with a deadly concoction of homemade wine and arsenic. While the circumstances here in Ronphibun, Thailand are entirely different, it highlights the dangers the heavy metal poses. Arsenic is known as the “silent killer”; it has no taste, no smell, no color, and can easily leach into surface and ground water without detection. While acute large doses lead to death within a few hours, arsenic is actually of greater public health concern in chronic low doses.
Chronic arsenic exposure is a major global environmental health concern and is estimated by the WHO to effect over 200 million people worldwide.1 Arsenic is found naturally in the environment, with some specific geographic areas like Bangladesh, India, China, and Taiwan having naturally arsenic-rich groundwater. However anthropogenic activities, primarily mining-related activities, have contributed to arsenic enrichment in certain areas of the world. Ronphibun Subdistrict, in Nakhon Si Thammarat Province of Southern Thailand, is one such area of high arsenic contamination.
Ronphibun literally translates into “rich in metals” because the area lies along the Southeast Asian tin belt and was heavily mined over the course of a hundred years. The tin-mining process left behind huge waste piles of arsenic-containing residue, primarily arsenopyrite. Usually arsenopyrite is underground, but when unearthed and exposed to oxygen the compound oxidizes and inorganic arsenic leaches into the surrounding environment. Here in Ronphibun, the arsenic leached into the local groundwater, surface water, and inhabitants’ shallow wells. To put the severity of the contamination into perspective, the WHO-recommended “safe” level of arsenic in drinking water is 10 μg/L and some of the shallow wells in Ronphibun contained over 1000 μg/L. The Thai government halted mining after over 1000 cases of arsenicosis were officially diagnosed in Ronphibun in 1987, and interventions like piped-in water from other areas and rain collection pots were distributed. Despite these interventions, the environmental and health impacts still persist today.
We are studying arsenicosis, the diseases associated with chronic ingestion of arsenic-contaminated water. Our focus is on one of the most common health effects that develop within years of exposure: arsenical skin lesions. These include:
- spotty or diffuse hyperpigmentation= dark spots
- depigmentation (or hypopigmentation)= white spots
- spotty or diffuse hyperkeratosis= thickened skin
These lesions can be precursors to Bowen’s disease and basal and squamous cell carcinomas. Keratosis is usually found on the palms or soles of feet, while hyperpigmentation and depigmentation are usually found on the arms, legs, and trunk. However, skin lesions type, pattern, and severity are extremely different among individuals, even those from the same household, and the reason is unclear. It is known that arsenic is excreted from the body through skin, hair, nails, and urine, but the mechanism that causes these arsenical skin lesions is not well understood.
Our study focuses on epigenetics, as it is likely that epigenetic changes to genes involved in melanin or keratin production have a role in producing these skin lesions. Led by Dr. Alan Geater and PhD student Witchaya (Morn) Phetliap of Prince of Songkla University (PSU) and Dr. Laura Rozek of UM SPH, the study investigates the role epigenetics plays in arsenical skin lesion manifestation and severity. We are comparing the epigenetics of Ronphibun residents with skin lesions and those without; Morn and I are collecting saliva samples for DNA analysis, and toenail and urine samples for long-term and short-term arsenic concentration analysis. Once we collect all the samples in Ronphibun, they will be brought back to Dr. Rozek’s lab for analysis.
This study has been a great collaboration between Thailand’s PSU and the University of Michigan; both schools recently signed an MOU to continue research collaborations together. I’ve had a great time interning in Thailand, so I am excited to for Morn to fly over and spend a couple months in Ann Arbor doing lab analysis for the project. I am sure he will receive a warm Michigan welcome (well… just a warm welcome from the people, not sure about the weather)!
Thanks to Marc-Grégor Campredon (http://www.marc-gregor.com) for providing the photographs.
1WHO (World Health Organization). Guidelines for drinking-water quality: incorporating first and second addenda to third edition. Vol. 1, Recommendations, Geneva: World Health Organization, 2008.