Experts divided over maximum mercury levels in human blood

Dewi Santoso and Sari P. Setiogi, Jakarta

The health scare in Pantai Buyat village in Minahasa, North Sulawesi, has raised the issue of mercury contamination, a topic over which experts differ when discussing safe levels in the human body.

According to the director of the University of Indonesia's Center for Environmental Safety and Risk Assessment, Budiawan, what is considered a safe level of mercury in the human body depends on a person's ability to tolerate the element.

"When talking about mercury, there is not a normal or abnormal level as it can vary in humans, depending on their lifestyles and diet," Budiawan told The Jakarta Post on Friday.

However, he said mercury was a foreign element that did not naturally exist in the human body and could be considered poisonous.

"But there is always the possibility that a person can be exposed to it (mercury), especially when a person is working in the metal industry," he said.

For such high-risk people, he said the American Conference on Government Industrial Hygiene had set the maximum standard for the total mercury level in the blood at 15 microns per liter (u/L).

"Thus, if we want to use common sense, the level of mercury in the average people's blood should be less than 15 u/L," Budiawan said.

He said that normally when the mercury level was higher than this, a person developed various symptoms, including nausea, massive weight loss and irritability, followed by nervous system- related problem or tremors.

Budiawan's explanation differed slightly from one given by Amin Soebandrio, an assistant deputy minister for medical and health sciences at the Office of the State Minister for Research and Technology.

According to Amin, the maximum safe level of mercury in human blood is 20 u/L. Anything higher could lead to health defects affecting the nervous and sensory systems.

"A study by the International Institute for Minamata Disease in Japan revealed that symptoms of contamination might show in people with mercury levels above 30 u/L," he told the Post.

The institute recommends that anyone with mercury levels of some 28 u/L go immediately to the health authorities.

To get a more accurate reading of mercury levels in the human body, according to Amin, a test on hair samples is required.

"The mercury level in the blood is very much affected by what someone has eaten within the last 30 hours. That means that if a person just ate contaminated fish, then the mercury level in his blood might be extremely high," he said.

Amin said that in victims of Minamata disease in Japan, the mercury levels obtained from their hair samples reached 7,000 u/L.

Minamata disease is a neurological disorder caused by methylmercury poisoning. It is known as the first major environmental disaster in Japan caused by humans.

Although mercury is the main cause of the disease, Amin said not all types of mercury contaminated the human body.

"There are three kinds of mercury: elemental, organic and inorganic mercury," he said.

Elemental mercury is the familiar liquid used in thermometers and barometers. "This type of mercury cannot be absorbed by the skin. Even if it is swallowed, it will only pass through the intestines," Amin said.

The dangerous types of mercury are the organic and inorganic types, he said.

According to the United States Agency for Toxic Substances and Disease Registry (ATSDR), organic mercury is formed when mercury combines with carbon.

Inorganic mercury is formed when the element combines with chlorine, sulfur and oxygen. This type of mercury can be found in industrial waste.

As dangerous as mercury is, there are also other hazardous elements that have been found in Buyat Bay: Cyanide and arsenic, both of which can cause death.

Amin said cyanide might be present in the water due to discharges from gold and silver and mining industries.

As for arsenic, it can be found in wood preservatives, pesticides, lead-acid battery from automobiles, rat poison and ant poison.

Arsenic has been recognized as a human poison since ancient times. Large oral doses of above 60,000 u/L can produce death, according to the ATSDR.

However, there is some evidence that small amounts of arsenic in a normal diet (10-50 u/L) may be beneficial for health.