Chemical in Boat Paint, Household Items Blocks Cancer-Fighting Cells

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Chemical in Boat Paint, Household Items Blocks Cancer-Fighting Cells

ANAHEIM, California, March 24, 1999 (ENS) - Anti-fouling paints used on boat

hulls, wood preservatives, even common household items such as cellophane

wraps and dish sponges have been found to contain a chemical compound that

disrupts the function of human natural killer cells. The job of these blood

cells is to destroy tumor cells and cells infected with viruses.

Kentucky researchers have demonstrated, for the first time, that a class of

common chemical contaminants known as butyltins disrupt the function of

critical human immune cells. The scientists say biologically significant

concentrations of butyltins were found in random human blood samples.

This information was presented Wednesday evening at a national meeting of

the American Chemical Society, the world's largest scientific society.

Murray State University chemist Bommanna Loganathan, Ph.D. performed the

study with another Murray State chemist, Margaret Whalen, Ph.D.

Loganathan says this current study, using blood cells from adult male and

female volunteers, is the first to demonstrate the effect of butyltin

compounds on human immune cell function.

Butyltin compounds come in either single, double, or triple forms. They are

used to inhibit the growth of unwanted organisms such as bacteria, algae,

and barnacles.

At shipyards such as this large quantities of tributyltin paints are applied

to vessels daily.

Tributyltin (TBT) is used as a wood preservative as well as on fish culture

nets, docks, and boat hull paints. Though TBTs have been banned on small

boats for about a decade, they are still commonly used on large ships to

prevent the growth of marine organisms.

TBTs have been detected in seafood, such as fish and oysters collected from

coastal areas, and in dolphin carcasses and seabed sediments. This study,

however, is the first to focus on the effect of TBTs on the tumor-killing

cells of humans.

Other recent studies have suggested that tributyltin levels have decreased

in U.S. waters in recent years, and some studies suggest that seafood does

not contain enough tributyltins to cause human health problems.

However, Murray State chemists say statistics for production of butyltins

used in many everyday applications are not available.

According to the Extension Toxicology Network maintained by Cornell

University, Michigan State University, Oregon State University, and

University of California at , TBT by itself is unstable and will break

down in the environment unless it is combined with an element such as

oxygen. One of the most common TBT compounds is bis(tributyltin) oxide, or

TBTO. This form has been the subject of most TBT testing.

Other TBT compounds are used as disinfectants, fungicidal wood

preservatives, textile disinfectants, and stabilizers in PVC resin. Paper

and pulp mills, cooling towers, breweries, textile mills and

leather-processing facilities may also use some forms of TBT.

When exposed to " environmentally relevant " concentrations of tributyltin in

the lab for as little as an hour, Loganathan says the tumor-killing ability

of natural killer cells was inhibited. Mono and di-butyltins were found to

be only slightly less harmful to the natural killer cells.

Loganathan and Whalen say that mono and dibutyltins are found in a variety

of household products including some types of diaper covers, sanitary

napkins, shower curtains, gloves, cellophane wraps, dish sponges, wines,

fruit juices, and poultry.

Loganathan and Whalen note that the human body can degrade butyltins fairly

efficiently and eliminates them in 24 to 48 hours. But, previous studies in

rats have shown butyltins to have various toxic effects, including

disruption of the immune system.

Alternatives exist. Treeline Wood Products Ltd. of Alberta, Canada uses a

borate-based process for wood preservation. Borates are effective pesticide,

fungicide and fire retardants and the company says they are " non-toxic to

humans, animals and the environment. "

The researchers also measured butyltin levels in the blood of eight people

who Loganathan says should have had no extraordinary exposure to butyltins.

He says he found " concentrations, in some cases, approaching levels where we

saw inhibitory effects on natural killer cell cytotoxic function in the

lab. "

Seventy percent of the world fleet of ships uses a tributyltin paint system,

and there is a constant but very low release of TBT from the ship hulls.

But this source of tributyltins may be phased out shortly. The International

Maritime Organization is planning a global ban on the use of marine

anti-fouling paints containing tributyltin from 2003.

The International Maritime Organization (IMO), with 156 governments as

members, is a specialized agency of the United Nations responsible for

measures to improve the safety of international shipping and to prevent

marine pollution from ships.

The IMO's Marine Environment Protection Committee is currently drafting

regulations to prevent the harmful effects of the use of anti-fouling

paints, in particular those continuing tributyl tin. The IMO aims to hold a

conference in the year 2000 to adopt the protocol.

In marine paints, a new generation of biocides allow antifouling paints to

protect ship bottoms from accumulating organisms while reducing

environmental effects.

Specialty chemicals manufacturer Rohm and Haas Company based in

Philadelphia, Pennsylvania, is one company that has developed an alternative

to tributyltin in marine paints for large commercial vessels. SEA-NINE® 211

marine antifoulant employs isothiazolone chemistry as a more environmentally

acceptable ingredient in marine paints. The new marine antifouling agent was

rewarded with the " Green Chemistry Challenge Award " from the U.S.

Environmental Protection Agency in 1996.

© Environment News Service (ENS) 1999. .