To understand how lead and other hazardous metals affect
our lives, Smith takes a big-picture approach. He traces the
chemical fates of metals in the environment and in our bodies.
Of all the industrial threats to public health, one of the most insidious
is lead poisoning. This toxic metal harms the brain in subtle ways, especially
in children. An aggressive effort in the U.S. to erase lead from paint and
gasoline has relegated the dark days of severe lead poisoning to the past.
However, researchers now suspect that even modest levels of lead in the
blood can cause long-term developmental damage. This "silent"
lead poisoning is hard to detect and harder to control.
Toxicologist Donald Smith, hired by UCSC's Biology Department last fall, thinks this problem won't soon go away. "We've won the war against lead for the general population," he says. "But all the lead we've discharged into our environment is still there, particularly in the inner cities. There's a lot of lead-based paint in older housing and in urban soils and dusts. In some cases this is a health threat to young children, because potentially any exposure is too much."
To understand how lead and other hazardous metals affect our lives, Smith takes a big-picture approach. He traces the chemical fates of metals in the environment and in our bodies. He explores where they reside in the body, for how long, and which varieties wreak the most havoc. Finally, he studies what happens to heavy metals in the body during clinical treatment for exposure. This research will help doctors evaluate the overall benefits of treatment.
Smith is part of "ETOX," a planned degree program at UCSC in environmental toxicology. The department promises to have national influence in this critical field. For Smith, his new position is like coming home: He earned both his bachelor's and doctoral degrees here.
Two of Smith's projects illustrate why many are excited about ETOX. First, he analyzes how the skeleton stores lead and also acts as a chronic source of lead exposure throughout life. Based on that work, Smith and his colleagues find that only about half of the lead in our blood comes from things we eat and breathe. The rest leaches from our bones, in which lead builds up over the years. This may pose health risks, especially in women whose bones deteriorate after menopause. Smith uses rats as model animals to examine how and why this process occurs.
Second, Smith contributes to a major study of an oral drug that removes lead from the body. Federal guidelines dictate the level of lead in a child's blood that warrants treatment with the drug, called succimer. However, some researchers question whether doctors should prescribe succimer for cases of "moderate" lead poisoning. The drug's ability to reduce toxicity in the brain isn't yet clear. Also, succimer may transfer lead to other parts of the body, compromising its effectiveness. Inspecting how the drug affects animals allows Smith and his coworkers to control for factors that confound studies in children, such as diet, habitat, income, and parents' IQ.
Midway through this five-year study, Smith sees some trends. "I wouldn't be surprised if we show that treatment is no more effective than simply removing a child's sources of exposure," he says. But with lead so pervasive in cities, he acknowledges, that solution may prove as elusive as the clouds of dust kicked into the air by children at play.
Robert Irion