Heavy metals are just what they sound like-heavy-with densities greater than 5 grams per cubic centimeter. Compared with water, which has a density of 1 gram per cubic centimeter, one can readily see that they are heavy indeed.

While small amounts of some heavy metals, such as zinc, copper and nickel, are necessary for human health, others-cadmium, chromium, mercury, lead, and uranium, most emphatically are not. Over time, exposure to even low dosages can be as harmful as more concentrated short-term hits.

Last year's blockbuster movie, "Erin Brokovich," graphically illustrates how one heavy metal, chromium, can wreak havoc on normal lives, causing- among other things, a variety of cancers and miscarriages, kidney, liver, and DNA damage. And like California, where the real-life story on which the movie is based unfolds, Ohio has its share of chromium, along with every other heavy metal you can name: lead, cadmium, mercury, nickel, copper, zinc, uranium.

In fact, Ohio ranks in the top 10 states in the nation for unacceptable levels of heavy metals. Ohio is third among all 50 states in mercury levels and second in copper release, with 336,480 lbs. released into the environment every year.

Worth Their Weight in Heavy Metal

Plant biologist Richard Sayre finds the problem of heavy-metal cleanup an intriguing challenge and is doing research that offers the promise of a safer, more effective, and relatively inexpensive solution. Sayre works with a species of metal-grabbing algae, Chlamydomonas reinhardtii, that acts like a sponge, soaking up and binding a variety of heavy metals, including copper.

"I got interested in this problem about five years ago," Sayre says. "Genetic engineering was just becoming possible for this kind of algae. I wanted to see what we could do to increase its metal-binding properties."

Concern about organic pesticides, such as PCBs and atrazine, sometimes obscures the dangers of heavy metals, which pose a tougher and greater remediation challenge. Since they cannot be broken down like pesticides, their removal becomes a difficult and expensive problem, restricting the kinds of technologies that can be used. Currently the global cost for heavy metal clean up and prevention is 30 billion dollars a year. It's been estimated that the bioremediation market in the United States alone will be 300 million dollars by 2005.

This is where Sayre's algae can come to the rescue. "These algae can be manipulated genetically to bind about 20 percent of their total weight. And once the metal binds to the algae, there are two possible outcomes," Sayre says. "They can be harvested, then recycled, which reduces the total amount of metal mined, smelted and released into the environment. Or they can be deposited in safe-site waste dump locations where they are unlikely to cause problems."

Sayre continues to explore lines of inquiry that allow him to attack the problem from different angles. He is working to identify peptides that bind to heavy metals from a combinatorial library of 1.3 billion different peptides. He plans to express fusion genes of a nickel-binding peptide and a plasma membrane peptide. "This will allow us to 'decorate' the surface of the cell with different peptides specific to certain metals," Sayre explains.

Sayre's work is funded by Ohio Sea Grant, part of the National Sea Grant Program, which has targeted the Great Lakes for major bioremediation efforts. Unfortunately, there are so many contaminated sites that only those with high concentrations or sites posing a direct threat to human, animal or plant life have been selected. Ohio has four such major sites where heavy metals enter Lake Erie-the Cuyahoga, Black, Maumee, and Ashtabula Rivers.

These new bioremediation techniques work equally well in soil and are also being used to remove uranium from the Fernauld waste site in Central Ohio.

Sayre believes the prognosis is good; things have improved since the first wave of pollution-consciousness hit in the late 60's. " Regulatory measures are better, standards have been set for acceptable contaminant levels, and education has improved-people are much more aware of environmental issues.

"But I want people to realize that biotechnology is not evil," Sayre says. "We think about safety all the time. One of our approaches is to use dead organisms, which are just as effective at removing the metals as the living tissue.

"There are so many advantages to the use of algae-they're renewable, there's not lots of energy input to produce them, they're non-toxic. In fact, there is no known environmental hazard associated with any of these species; they grow in soil, so they are everywhere. They're benign-using them is a safe way to go."