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Toxicants in the Environment: Are we being exposed? CDC's National Center for EnvironmentalHealthhelps provide the answers. ged enough and don't have the throughput we need," says James L. Pirkle, assistant director for science at EHLS. NCEH is just one of the many centers that make up the Centers for Disease Control and Prevention (CDC). Founded in 1946 in Atlanta, GA as the Communicable Disease Center, CDC got its start as part of the U.S. Public Health Service working with state and local health officials to combat malaria during WWII. In 1980 CDC created the Center for Environmental Health, which later became NCEH, to solve health problems related to substances in the environment. Today NCEH is the world leader in assessing human to environmental toxicants
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he phone is ringing off the hook. coming in from all over the world. An enviHundreds of people are dying, and ronmental health epidemiologist and an innobody knows why. Something has fectious disease epidemiologist are flown to to be done, and it has to be done immedithe scene to assess the situation. Blood and ately. This scenario is all loo familiar ro urine samples are collected and sent back to workers at the National Center for Environthe laboratory for immediate analysis. mental Health (NCEH), whose task is to Day in and day out, NCEH s Division 01 prevent death and disease that result from Environmental riealth Laboratory Sciences exposure to substances in the environment (EHLS) is faced with tremendous analytical Whether it's a natural disaster or a dangerchallenges. Because human life is at stake, speed is extremely important. Every day ous chemical spill, NCEH's emergency rethey must run multiple samples and look at sponse team is quick to respond to calls multiple analytes, often with only a small amount of sample to work with. Most new Britt Erickson analytical chemistry methods are not rug-
Method constraints In addition to being fast, the methods used at EHLS must be highly sensitive and specific. "We focus on biomonitoring—assessing exposure by measuring toxic substances and their metabolites in people." Levels in humans are generally 100-100,000x lower than levels in the environment. "Measuring substances in people requires much greater sensitivity," says Pirkle. "Generally, the levels we are measuring are in the pptr
Analytical Chemistry News & Features, December 1, 1998 797 A
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range, but occasionally they are in the ppq range." Specificity is equally as important, as very small changes in structure can dramatically alter a substance's toxicity. "We have to be sure that we are measuring what we say we are and not a compound's sister. If you take a chlorine off a dioxin ring, the toxicity changes 15,000-fold." EHLS is equipped with state-of-the-art instrumentation, including about 20 mass spectrometers. Expensive equipment is a necessity for the type of work they do. "First we develop techniques using our instrumentation, and then we simplify them down, if possible, so that we can transfer them out to other laboratories," says Pirkle. State public health laboratories arc the primary recipients. Over the past 18 years, researchers at EHLS have developed methods for measuring more than 250 toxic substances in people, including dioxins and furans, PCBs, pesticides, VOCs, PAHs, ,ead, cadmium, mercury, uranium, thorium, and other metals. "We have those methods on the shelf. .I something happens related to any of those compounds, we can use them to figure out who was exposed," explains Pirkle. .A lot oo times it's just assuring people that they have not been exposed. For those that have been exposed however we have to be able to measure the dose and toxicity is dose" All of the methods are designed to run at least 40 samples per day. "Not 40 one day, and the instrument goes down for two weeks. It's 40 samples every day," emphasizes Pirkle. "We have to have rugged methods. You can't run dirty samples
through an instrument because it will cause it to go down. The cleanup has got to be much better, yet we have to be fast." To overcome the throughput problem, Donald Patterson and co-workers at EHLS's Toxicology Branch have turned to highspeed single-dimensional and multidimensional GC. "By using two GC columns, we can analyze 17-18 nonpersistent compounds in less than 5 min. .n comparison, with only one column it takes 45-50 min," says Patterson. In 2-D GC one column contains a polar stationary phase and the other a nonpolar phase "What doesn't get separated in the first dimension gets separated in the second " In addition to being faster 2-D GC is also more sensitive than 1-D GC "The Dcaks are compressed into very narrow peaks increasing the S/N You increase your sensitivity SDecificitv and
used as a 'gold standard' to determine if people have been exposed to more than the general population," says Larry Needham, chief of EHLS's Toxicology Branch. One such study is the National Health and Nutrition Examination Survey (NHANES). CDC has been the primary laboratory involved in NHANES for more than 20 years, measuring levels of vitamins and trace elements, such as zinc, copper, selenium, and iron, as well as other analytes related to nutritional deficiency in people, says Elaine Gunter, chief of the NHANES laboratory. "For the first survey we had only 10-12 methods. For our most recent survey, NHANES IV, we have 65 different methods."
aerosol formation or distribution of the solid. We work wiih extremely small quantities, but we don't know the purity of the material, how concentrated a solution of it may be, or even how toxic it may be."
low are just a few examples. EHLS has set the world's standard for measuring cholesterol and lipids that relate to coronary artery disease. Over the years, drey have developed reference methods and reference materials for measuring cholesterol and have developed a program to offer the standardization services to various laboratories. 'We have a major effort in making sure all cholesterol measurements are done well, with low CVs [coefficients of variation] and high accuracy. We standardize about 90% of the manufacturers who make kiis and instruments to measure cholesterol. The
NHANES involves monitoring ~ 30,000 people over a six-year period. "We conduct an extensive interview in their homes, and then we bring them into our mobile exam Because the chemical compositions of centers for a three-hour head-to-toe physitoxicants are often unknown, precautions cal," says Gunter. Altogether, about 85 biomust be taken, says Helen Schurz Rogers of chemical tests are performed on their EHLS's Toxicology Branch. "For example, we are looking at Pfiesteria toxins." Pfiesteria blood, urine, and hair. The levels of virtually everything in a person's body are meapiscicida, a microbe that has been linked to sured. "When we are done we have over fish lesions and massive fish kills in North Carolina and Maryland, is suspected of caus5000 different variables in a database ing skin irritations and memory loss in hueverything from what kind of health insurmans. "We have no strong evidence of the ance a person has to what kinds of vitaroute of exposure. When we are working mins they take" with unknown toxins, however, we take precautions to minimize possible exposure Further down the road through inhalation or dermal contact." When they are not responding to emerSchurz Rogers and her co-workers always gency situations, researchers at EHLS are wearTwek suits and respirators when work- busy working on ways to prevent long-term ing with materials isolated diseases. They have been involved with piscicida "Wetrvto numerous studies, far too many to list. Be-
Analyst runs five chromatographic separations at a time. 798 A
What is normal? Before you can diagnose someone as having abnormally high levels of a toxicant, you have to know what is normal. EHLS is involved in reference range studies to determine what is normal for the U.S. population. "Those values can be taken and
Analytical Chemistry News & Features, December 1, 1998
base for all of the major cholesterol studies in the world is in our laboratory" says Pirkle
Another group is focusing on measuring end products of tobacco use in people. Cotinine, a metabolite of nicotine, is commonly used to monitor exposure in active and passive smokers. "Cotinine is used because it's derived directly from nicotine. It's very specific for tobacco and it has a much longer half life" riains Tom Bernert "Cotinine has been
Schurz Rogers takes precautions against Pfiesteria toxins.
meamirpH for a lono* time There are a lot of methods vnn can u
