Research Ties Arsenic to Tumor Growth

The study is significant for residents of central Oklahoma, which has some of the highest arsenic levels in drinking water in the nation.

Michael Ihnat, an assistant professor of cell biology who headed the research team, said researchers still do not know whether arsenic in drinking water increases the overall incidence of tumors.

"What we can say pretty definitely is that if you have a pre-existing tumor, and you're drinking water with arsenic in it, it could very well increase the growth of that tumor," Ihnat said.

The study shows that arsenic levels as low as four parts per billion stimulated blood vessel growth, while levels as low as 10 ppb caused tumors to expand.

The current federal arsenic standard is 50 parts per billion, but that standard is being lowered to 10 parts per billion on Jan. 23.

The Environmental Protection Agency will present the study to a congressional subcommittee in November "to really drive home that they need to reduce the standard to 10 ppb," Ihnat said.

"Between that ten and 50, a lot goes on that's not good," he said.

When environmental arsenic is ingested, it reacts with oxygen to create free radicals — very reactive forms of normal molecules — which then stimulate blood vessel growth, Ihnat said. An expansion in blood vessels means an increase in blood supply to the tumors, which then grow larger, he said.

Ihnat and his team used mice to conduct the study. For five weeks, they fed the mice water with arsenic levels between 10 ppb and 200 ppb, and then implanted cancerous tumors on the animals.

The researchers continued to give them the arsenic water and monitored the tumors' growth for six more weeks. At the conclusion, Ihnat's team found that the arsenic increased the growth rate of the tumors, as well as causing the tumors to spread to the lungs.

Ihnat's study did not conclusively link arsenic ingestion and the development of cancer, although many studies have tied the two together_ particularly arsenic to the development of skin and bladder cancer — said Monty Elder, spokeswoman for Oklahoma Department of Environmental Quality.

However, the Oklahoma State Department of Health, which tracks cancer cases, has not found clusters of either skin or bladder cancer anywhere in Oklahoma, said Anne Bliss, epidemiologist at the health department.

Arsenic in Oklahoma's water occurs naturally and is generally found only in groundwater systems, Elder said.

There are 1,290 groundwater systems in Oklahoma that serve 700,000 people, mostly in rural areas, Elder said. DEQ predicts 25 of those systems — including Norman, Yukon, Mustang, Weatherford and Nichols Hills — will have problems meeting the new federal standard of drinking water, she said.

Elder said it will cost between $55 billion and $163 billion to replace or upgrade the 25 systems.

The majority of the state's population — 2.8 million people, or 79 percent — are served by 233 surface water systems, which do not have problems with arsenic levels, she said.

Ihnat said there is little central Oklahoma residents can do to avoid arsenic-tainted water other than buying bottled water.

"None of the standard filters filter arsenic to any great degree because it's an element, an ion," Ihnat said. "It's very hard to get out."

High dollar filtration systems, such as the reverse-osmosis filter, can rid water of arsenic, but Elder said the expense outweighs the cost of digging a new well or importing water from another area.

Ihnat said his next step is to discover if arsenic levels increase the risk of developing tumors, and if the process can be interrupted or reversed. He predicted it will take another year before he has answers.

"If we can do that, then I think we're helping out," Ihnat said.

Reference Source 102
August 10, 2005

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