Tests conducted by the International Agency for Research on Cancer (IARC) and kept from the public for nine years have revealed higher levels of carcinogen damage in the DNA of Map Ta Phut residents than people living elsewhere.

The World Health Organisation's IARC and the National Cancer Institute of Thailand (NCI) studied carcinogen damage in DNA of industrial estate employees and nearby residents in 1998.

Until now, the results of this team's study have been kept quiet.

It conducted tests on 81 estate workers, 71 residents and 50 people from other districts in Rayong.

It found the "DNA adducts" ratio in industrial complex workers and nearby residents was 1.9 and 1.4 times higher greater than that in people not living in the estate.

The difference in ratio between the two exposed groups was not statistically significant.

"Our results suggest occupational and environmental exposures experienced in industrialised areas of Thailand might entail an increased level of DNA adducts," a research summary obtained by The Nation said.

The results did not identify the agents responsible for the increased levels.

DNA damage caused by carcinogens - or DNA adducts - occurs when compounds attach themselves to DNA molecules.

Paolo Boffetta of the IARC and the NCI's Petcharin Srivatanakul led the research.

Srinakharinwirot University Medicine Faculty occupational diseases expert Dr Chatchai Ekpanyaskul said DNA adducts could be an indicator of risk of cancer. However, he said it was hard for doctors to specify the carcinogens and sources because DNA adducts - like cancer - could be caused by combined exposure to more than one carcinogen.

Chatchai has spent years monitoring the risk of cancer associated with occupation and environment. He was not involved in the IARC research. But, he was convinced Map Ta Phut people had a higher risk of developing cancers than people living elsewhere.

An NCI source revealed its study had never been released.

That was because it was conducted in the same year as the Pollution Control Department (PCD) monitored air in the area and reported volatile organic compounds at Map Ta Phut were no higher than acceptable levels.

"If the research was released at that time it would not have been accepted because it did not accord with the PCD air-quality data," the source said.

"It seemed the paper was groundless because we found results but no cause."

He believed the research might be released soon together with the results of the second phase of the NCI study. That counts the number of Map Ta Phut people suffering from cancers.

Recorded cases of cancer in Rayong residents between 1997 and 2001 show Map Ta Phut residents present 182 cases in every 100,000 people.

Seven in every 100,000 contract leukaemia. That is two to three times above the national average.

Phase two collected cancers recorded between 2002 and 2005. "If the number of cancer cases in the second period is higher than the first we can conclude they are associated with volatile organic compounds released from the factories," said Petcharin from the NCI and IARC study team.

Students and teachers at Map Ta Phut's Phan Pittayakarn School fell ill in 1997 with acute respiratory problems. But the PCD insisted toxic chemicals present in the air were no greater than acceptable standards.

The Public Health Ministry asked agencies, including the NCI, to dig deeper. The results have been under wraps since then.

But, in October 2005, Greenpeace Southeast Asia and the Campaign for Alternative Industry Network presented "shocking findings" from a five-month-long investigation.

They found "extremely-dangerous" levels of air pollution, including carcinogens, in all air samples taken from areas of Map Ta Phut and its industrial estates.

Volatile organic compounds detected included benzene, recognised by the IARC as a leukaemia-causing carcinogen, vinyl chloride, an agent that can cause liver, brain and lung tumours, and 1,2-dichloroethane, commonly known as ethylene dichloride which can cause lymphatic and hematopoietic cancer.

The findings prompted the then Environment Minister to ask the PCD to do more tests.

Three months later the PCD reported 40 volatile organic compounds contaminated the area's atmosphere. Nineteen were carcinogenic and average 24-hour levels exceeded United States Environmental Protection Agency maximums.

Some were identified by the IARC as carcinogens, some "probably carcinogens" and some "not yet classified" (see graphic).

The PCD findings led to recent attempts to declare Map Ta Phut a pollution-control zone under the Environmental Protection Act.

If these had succeeded, environmental agencies could intervene in the management of industrial estates in the area. That is presently in the hands of the Industrial Estate Authority of Thailand.

A control zone will force factories to reduce emission levels to acceptable standards.

But, rather than declare a pollution-control zone the National Environmental Board set up two committees to study the relationship between residents' illnesses and pollution.

Now, Petcharin hopes the hidden 1998 study will convince the NEB to declare the proposed control zone.

Located in Muang Rayong district, Map Ta Phut is home to almost 100 factories on four estates - Map Ta Phut, Pha Daeng, Eastern and Asia. Most are petrochemical and power-generation plants. Some are coal fired.

There are chemical-fertiliser factories, oil refineries and toxic-waste-treatment plants, too.

Pennapa Hongthong

The Nation