Thailand dismisses chlorpyrifos as cause of Chiang Mai hotel tourist deaths (video)

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Thailand public health authorities have dismissed claims made by New Zealand 60 Minutes that the widely-used chemical agent chlorpyrifos is behind the deaths of a number of tourists at the Downtown Inn in Chiang Mai earlier this year.

The New Zealand current affairs programme, supported by United Nations scientist Dr Ron McDowall, made the claim in an episode titled To Die For, with Dr McDowall saying he believed the dead Chiang Mai tourists had been killed by an overzealous fumigator who’s been acting on the instructions of the hotel owner to deal with bed bugs.

Dr McDowall said he had consulted with other experts in New Zealand and Italy and all agreed the likely cause of death of the seven was from excessive exposure to pest control chemicals.

Chlorpyrifos not the cause of Chiang Mai tourist deaths

However, a statement issued by the Department of Disease Control (DDC), Ministry of Public Health (MOPH) and the Chiang Mai provincial authorities, titled ‘International toxicologists consulted in Chiang Mai tourist deaths – Update 3‘ said ‘toxicology experts had reviewed the available evidence and discussed several possible causes involving toxins and chemical agents as a cause of death.

60 Minutes New Zealand reporter Sarah Hall is seen taking samples from the air-conditioner in The Downtown Inn hotel room that Sarah Carter stayed in Chiang Mai
60 Minutes New Zealand reporter Sarah Hall is seen taking samples from the air-conditioner in The Downtown Inn hotel room that Sarah Carter stayed in Chiang Mai

‘This included the suggestion made by the New Zealand TV’s 60 Minutes programme that chlorpyrifos was responsible for the death of New Zealander, Sarah Carter, and the illness of her two travelling companions. Laboratory investigations do not support chlorpyrifos as a cause’.

‘Though a cause has not been clearly identified to date, experts recognised that chlorpyrifos generally emits a strong odor which was not noted by the two surviving women. They also noted that chlorpyrifos is not well absorbed by the skin, nor would it cause rapid illness or death in a healthy adult unless it was ingested or inhaled in very high quantities.

‘The toxicologists are also considering the possibility that other chemical agents, including those found in pest control products might cause signs, symptoms, and laboratory findings consistent with the features seen. Experts are also currently working to identify the most suitable laboratories to carry out specific tests for selected pest control ingredients in the remaining samples.

Toxicology assessments underway

The statement said the investigatory group had sought the assistance of international toxicology experts earlier this month to determine whether toxins or chemical agents might be involved in the deaths, along with the associated illnesses of three other individuals centered around the Downtown Inn in Chiang Mai earlier this year.

‘Concurrently, environmental and toxicology assessments involving experts and laboratories from the Department of Health, MOPH; Ministry of Agriculture; Ramathibodi Poison Center; the Faculty of Agriculture, and Chiang Mai University (CMU) are underway at the hotel where the four persons died’, the report states.

International brief meeting update clusters of death with unexplained cause in Chiang Mai
International brief meeting update clusters of death with unexplained cause in Chiang Mai

The report covers five deaths in Chiang Mai and said the people who died and fell ill are being examined in three groups based on the hotels they stayed in as follows:

  • Soraya Pandola (age 33) who died on January 11, 2011 and her Canadian colleague (age 29) who fell ill
  • An unnamed French woman (age 25) who died on January 19, 2011
  • Waraporn Pungmahisiranon (age 47), a Thai tourist guide, who died on February 3, 2011
  • Sarah Carter (age 23) who died February 6, 2011 and her two companions (both age 23) who both fell ill
  • George and Eileen Everitt, (age 78 and 74) who both died on February 19, 2011

According to the report: ‘Based on findings currently available there is insufficient evidence to link the illnesses and deaths among these three groups. The American, Canadian, and French woman had no activities in connection with other hotels and other cases. The French women also began to fall ill few days before arrival in Chiang Mai’.

Experts from five countries called-on to solve Chiang Mai death hotel riddle

The report said the assistance of expert toxicologists have been sought as part of the ongoing investigation into the Chiang Mai tourist deaths, including experts in Australia, the United Kingdom, the United States, India, and Sri Lanka. In addition, the World Health Organization (WHO) and the US Centers for Disease Control and Prevention (US-CDC) have also been recruited to assist.

Chiang Mai Provincial governor Mom Luang Panadda Diskul has maintained the Chiang Mai tourist deaths are "a coincidence" – and so far there is nothing to prove otherwise
Chiang Mai Provincial governor Mom Luang Panadda Diskul has maintained the Chiang Mai tourist deaths are “a coincidence” – and so far there is nothing to prove otherwise

The assistance of these toxicologists was sought following a meeting of clinicians, epidemiologists, pathologists, toxicologists, laboratory specialists, police, the WHO and the US CDC in Chiang Mai on May 10, 2011.

The report says an initial assessment of overnight room ventilation in April found adequate air ventilation with normal levels of nitrogen dioxide and sulfur dioxide; and no evidence of carbon monoxide accumulation.

According to the report the investigation has so far found few common traits except that:

  • All occurred in Chiang Mai between January 11 and February 19, 2011
  • Six of the nine reported people affected lodged at one hotel (three were at two different hotels)
  • The first six people identified are young (aged 23 to 29) female, non-Thai nationals

The report notes that a Canadian man who died in January, Bill Mah, aged 59, from Alberta, Canada, may have used the swimming pool of the hotel where the Thai woman, the New Zealand women, and the United Kingdom couple stayed, the Downtown Inn, Chiang Mai. However, it has not been possible to confirm these reports or even to establish the day when this visit was supposed to have occurred.

Post mortem examinations fail to establish link

Of the postmortem and pathological examinations conducted, the report states: ‘the available evidence from medical records and autopsy by forensic expert do not currently support linkage with other deaths. Therefore the death of this man (Mr Mah) has not been included in the cluster’.

According to the statement ‘it was initially believed on the basis of clinical findings that myocarditis (inflammation of the heart muscle) was a common factor in a number of deaths. However, although it is clear that heart muscle damage occurred in these cases, further investigation of clinical, laboratory, and histopathology records, has only established clear evidence of myocarditis in the case of the French woman.

The Downtown Inn, Chiang Mai, Thailand
The Downtown Inn, Chiang Mai, Thailand Hotelopia

‘It is partly this evidence that has resulted in the scope of the investigation being widened to look for other causes of cardiac damage (that can mimic the clinical appearance of myocarditis), including toxins and chemical agents.

‘A final explanation of the most likely cause of the event(s), including exact cause of illnesses and deaths, and any important related factors, will be made based upon the synthesis of evidence from clinical, epidemiological, laboratory, environmental, and forensic investigations.

‘It is important to highlight that a complex investigation such as this, which also includes international laboratory analyses takes time. Any new toxicology results are also likely to take time if specimens need to be shipped to specialist laboratories.

‘It is also possible that cases may not all be linked, and may instead be due to different causes.

‘Despite the best efforts of Thai authorities and international partners, a complete explanation for the cause of deaths may not be found for all cases’, the report concluded.

The statement said the Thai Ministry of Public Health will provide information as it becomes available. To date they have proven very willing to do so.



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John Le Fevre is an Australian national with more than 40 years experience as a journalist, photographer, videographer and editor.

He has spent extensive periods of time working in Africa and throughout Southeast Asia, with stints in the Middle East, the USA, and England.

He has covered major world events including Operation Desert Shield/ Storm, the 1991 pillage in Zaire, the 1994 Rwanda genocide, the 1999 East Timor independence unrest, the 2004 Asian tsunami, and the 2009, 2010, and 2014 Bangkok political protests.

In 1995 he was a Walkley Award finalist, the highest awards in Australian journalism, for his coverage of the 1995 Zaire (now Democratic Republic of Congo) Ebola outbreak.

Most recently he was the Thailand editor/ managing editor of AEC News Today . Prior to that he was the deputy editor and Thailand and Greater Mekong Sub-region editor for The Establishment Post, predecessor of Asean Today.

In the mid-80s and early 90s he owned JLF Promotions, the largest above and below the line marketing and PR firm servicing the high-technology industry in Australia. It was sold in 1995.

Opinions and views expressed on this site are those of the author’s only. Read more at About me

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9 Responses to "Thailand dismisses chlorpyrifos as cause of Chiang Mai hotel tourist deaths (video)"

  1. guyinthailand   July 11, 2012 at 9:31 pm

    ‚Äú … and noted that chlorpyrifos, is not well absorbed by the skin, nor would it cause rapid illness or death in a healthy adult unless it was ingested or inhaled in very high quantities”.

    Look how misleading the above statement from the Thai ‚Äòauthority‚Äô is. In fact, as little as one TEAspoon of chlorpyrifos (an insecticide) if ingested can cause death. Inhalation and skin exposure has to be in high quantities–true. But not ingestion. It is obvious the Thais will do everything they can think of to deflect attention away from the most likely explanation: murder by pesticide.

    Thais routinely use pesticides to commit suicide and homicide and in 2012 a Thai was arrested who was slipping a methomyl, an insecticide, in the coffees of drivers to kill them to steal their cars for a car theft ring who paid him $300 per car. He killed approximately 6 people (haven’t found some of the bodies).

    The symptoms and deaths on Phi Phi (2009 and 2012) and Chiang Mai (2011) do not correlate with 1) food poisoning, 2) party drugs 3) toxic seafood 4) dengue and other related fevers 5) alcohol 6) visine 7) GBH 8) water treatment plants 9) cholera and 10) mushrooms. Other than aluminum phosphide, most pesticides do not reliably kill by inhalation or skin exposure, and even if aluminum phosphide was shown to be the culprit it is next to impossible to have been accidental because we would see many, many more truly accidental deaths from this highly toxic poison if it were routinely used in the tens of thousands of hotel rooms in Thailand to kill, for instance, bed bugs.

    Therefore, you don’t ‘get’ cyanide or aluminum phosphide poisoning ‘accidentally’ in this many victims and it is very, very difficult to get other kinds of poisoning ‘accidentally’ such that it will kill you immediately. Most poisons have to be ingested to be lethal.

    The kind of poisons that can kill with the ingestion of as little as a teaspoon (chlorpyrifos, cyanide, methomyl) or a tiny piece of a 3 gram tablet (aluminum phosphide) are readily available in Thailand and are used by Thais in homicides and suicides.

    Numerous posters, myself included, on various discussion boards have related stories of their own deliberate poisonings while in Thailand, often from disgruntled restaurant workers after complaining about the food or service. (Always carry activated charcoal in your travel kit and swallow a handful at first sign of feeling unwell. Activated charcoal, available in every Thai pharmacy, is THE number one poisoning protocol in emergency rooms worldwide for most types of poisonings). Thailand has a very high murder rate and many murderers are caught but are set free, and Thailand is known for the 100 or so ‚Äòhitmen‚Äô–killers for hire–that roam free. Just like the Thai serial killer using methomyl in his Thai victim‚Äôs coffees to steal their cars to earn $300 per car from a car theft ring, surely there are other serial killers in the Land of Smiles who are doing this for kicks or revenge.

    Phuket and Koh Phi Phi are controlled by some very deviant, violent mafia-types who get easily angered when Westerners ‘challenge’ them. And it must always be remembered that the killer(s) do not have to be Thai.

    Let’s all quit pretending that Thailand is the only country in the world without serial killers. Just because you don’t often hear about them in the Thai media only means the Thais don’t do thorough investigations and, if they were to actually find one who was killing tourists, would very likely cover it up to protect their billion dollar tourist business.

    To rule out a (serial) killer without a full investigation is a mistake no Western detective would make–unless the evidence was overwhelming.

    Until proven otherwise, these deaths—Phi Phi (May 2009 and June 2012) and Chiang Mai 2011 were no ‘accidents’.

  2. banphai   August 16, 2011 at 8:43 am

    The final report of the Thai Department of Disease Control has just been released. Here its is in full (I only have the report file, not the URL, but my source is:

    • John Le Fevre   August 17, 2011 at 7:11 pm

      Thanks very much Peter.

      Your post arrived at the same time as I was wading through the various documents. I’ve truncated your post as it was a bit long to leave in the comments section. Please see Chiang Mai tourist death probe finds no common link

  3. banphai   August 5, 2011 at 7:39 am

    This article appeared in the NZ Herald this morning – still no closure!

    I can only hope that the NZ Ministry of Foreign Affairs and Trade receives a copy of the full report by the Thai panel of experts and forwards it to Mr Carter for him to release. I, for one, will be most interested to see details of the tests performed and the results, and how the panel arrives at its conclusions.


  4. banphai   July 2, 2011 at 1:30 pm

    The last official update on the investigation by the Thai Ministry of Public Health was 21 June and can be accessed here:
    It now appears that the overseas test results are known (and seem inconclusive):

    • John Le Fevre   July 2, 2011 at 3:45 pm

      Thanks very much Peter.

      I’m still trying to find a site with the report I can download or view.

  5. banphai   June 20, 2011 at 5:44 pm

    What happened to the results of the international laboratory analyses? Just how long can this possibility take?

  6. banphai   May 26, 2011 at 9:18 am

    The New Zealand Ministry of Foreign Affairs seems to be less than impressed by the latest report from the Thai public health authority – see last paragraph of this article in today’s Dominion Post:
    Thais deny tourists’ deaths linked

    It’s hard to disagree with the view of Sarah Carter’s father that Thai officials have appeared to be more concerned with shearing up the tarnished reputation of a Chiang Mai hotel than with determining the cause of the deaths. The irony is that even the attempts to exonerate the hotel have proved to be a shambles.

  7. banphai   May 25, 2011 at 6:50 pm

    I very much doubt that this latest statement by the Thai health authority will do much to reassure the families of the deceased about the possible role of chlorpyrifos poisoning.
    Most of the technical reports available on the internet describe the odour of this organophosphate as ‘mild’, and there are certainly low odour chlorpyrifos products on the market (eg Lorsban Advanced) which can easily be masked by air-fresheners. These are widely used in Thailand and would allow time for the inhabitants of a room to adapt to any low sulphur-like odour of chlorpyrifos. Olfactory adaptation can be very rapid.
    This seems to be yet another attempt at obfuscation by the Thai investigators. Chlorpyrifos poisoning can be diagnosed from the presence of a breakdown product in urine (3,5,6-trichloro-2-pyridinol) or it can be presumed from reduced levels of cholinesterase found in fresh blood samples. The key issues are therefore whether the appropriate blood and urine samples were correctly taken and stored and, if they were, what has merged from the analyses.


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