Dangerous dental sealants?

allow three different levels of carbon dioxide to be maintained, with identical plants grown in each section. Broecker said they are looking at conducting long-term experiments (perhaps decades-long) that emphasize perennial plants. They will look at factors such as the quality of fruits and nuts, as well as water-use efficiency. Many questions remain about what experiments to conduct, what plants to study, and how to conduct studies, Broecker said. "We want to use the bios-phere for things we can't do elsewhere," he said. "It would be silly to use this expensive structure for experiments that could be done in smaller labs." For example, the ocean biome of Biosphere 2 offers a unique opportunity to study oceanic phenomena in a controlled setting. Researchers plan to study the effects of rising carbon dioxide on the growth of coral. "This is something we can do that others can't," Broecker said. In searching for the best ways to use Biosphere 2 for scientific purposes, the Columbia management is welcoming input from other scientists. "We have to explore other people's opinions about the validity of what we want to do," Broecker said. "I think the success of the place requires that we make close ties with experts from around the world. That gives us more credibility and prevents us from making dumb mistakes." Columbia officials have been collaborating with the University of Arizona and Arizona State University. Broecker said that the information highway is bringing universities in closer contact with one another to work on projects such as Biosphere 2. "We hope to make Biosphere 2 a center for plant physiology," he said. In addition to directing research at Biosphere 2, Columbia will also introduce educational programs. These include a college level program in earth and environmental sciences, a "semester abroad" program in which students from around the world can conduct research at the bios-phere, an earth sciences curriculum linked through the World Wide Web, and teacher workshops. Columbia also plans to expand the science and visitors' center, which will be open to the public. No more live-in missions are planned for Biosphere 2 at this time, according to university officials. The use of dental sealants containing bisphenol-A-related compounds should be reevaluated, according to researchers at the A fter World War II, impoverished people throughout the world were suffering A from health problems such as chronic malnutrition, communicable diseases, and parasitic infections, and many people …

allow three different levels of carbon dioxide to be maintained, with identical plants grown in each section.
Broecker said they are looking at conducting long-term experiments (perhaps decades-long) that emphasize perennial plants. They will look at factors such as the quality of fruits and nuts, as well as wateruse efficiency.
Many questions remain about what experiments to conduct, what plants to study, and how to conduct studies, Broecker said. "We want to use the biosphere for things we can't do elsewhere," he said. "It would be silly to use this expensive structure for experiments that could be done in smaller labs." For example, the ocean biome of Biosphere 2 offers a unique opportunity to study oceanic phenomena in a controlled setting. Researchers plan to study the effects of rising carbon dioxide on the growth of coral. "This is something we can do that others can't," Broecker said.
In searching for the best ways to use Biosphere 2 for scientific purposes, the Columbia management is welcoming input from other scientists. "We have to explore other people's opinions about the validity of what we want to do," Broecker said. "I think the success of the place requires that we make close ties with experts from around the world. That gives us more credibility and prevents us from making dumb mistakes." Columbia officials have been collaborating with the University of Arizona and Arizona State University. Broecker said that the information highway is bringing universities in closer contact with one another to work on projects such as Biosphere 2. "We hope to make Biosphere 2 a center for plant physiology," he said.
In addition to directing research at Biosphere 2, Columbia will also introduce educational programs. These include a college-level program in earth and environmental sciences, a "semester abroad" program in which students from around the world can conduct research at the biosphere, an earth sciences curriculum linked through the World Wide Web, and teacher workshops. Columbia also plans to expand the science and visitors' center, which will be open to the public. No more live-in missions are planned for Biosphere 2 at this time, according to university officials.

Dangerous Dental Sealants?
The use of dental sealants containing bisphenol-A-related compounds should be reevaluated, according to researchers at the University of Granada and Tufts University.

HEamH AROUND THE WoRLD AND THE NET
A fter World War II, impoverished people throughout the world were suffering A from health problems such as chronic malnutrition, communicable diseases, and parasitic infections, and many people did not have access to health care. In response to the perceived need for a world organization to group resources for health, develop hea goals, and provide a forum for the exchange of health information, the United Nations set up a specialized agency-the World Health WHO is headquartered in Geneva, Switlad, with satellite offices located throughout the world. WHO's World Wide Web site is located at URL: http://www.who.ch and provides background information, current WHO projects, and WHO's future plans. The WHO home page offers 17 links to health and health-ilaitd information, as well as to statistical and epidemiological data.
The link to Headquarters' Major Programmes lists the more than 30 divisions of WHO, with links to most of these programs. Among these are the Division of Control of Tropical Diseases, the Division of Family Health, the Division of Food and Nutrition, the Global Programme on AIDS, and the Division of Health Promotion, Educaton, and Communication. There is also a link that provides information about WHO field offices.
The link to the World Health Report 1995 offers the executve summary of the report, which discusses gaps in health and access to health care. From this site, a link to 50 Facts of Health lists statistics and highlights from the report. For example, according to 50 Facts, "it is estimated that by the year 2000, over 5 million children will be infected by HIV and another 5-10 million orphaned by the HIV/AIDS pandemic." Another link accesses the Weekly Epidemiological Report (WER), which provides timely epidemiological information on cases and outbreaks of diseases under the Intro nal Heah Regulations. The report also describes other communicable diseases of public health importance, induding newly emerging or reemerging infections, noncommunicable diseases, and other health problems. The WER is distributed electronically every Friday in English and French.
The WHO Web site also serves as a useful tool for research on. health-related information. The link to the WHO Statistical Informaton System (WHOSIS) provides selected health and health-related statistical databases and pointers to additional 'WHO information. The link to public information offers press releases, newsletters, publications information, and library information. An Outbreaks link provides information on outbreaks of diseases such as influenza and Ebola. There are also links to World Health Day and World No-Tobacco Day both of which are sponsored by WHO. For travelers, tie link to Intemational Travel and Health offers vaccination requirements and health advice. Other links are still under construction, but most are up and running. Forum Nicolas Olea and colleagues reported in the March 1996 issue of EHP that resin-based composites and sealants may contribute to human exposure to xenoestrogens.
The American Dental Association (ADA) endorses the use of dental sealant, a thin plastic coating, to prevent cavities. The cleaned tooth is roughened with an acid solution. Sealant is then painted on the tooth enamel and cured, or hardened, by either chemical reaction or light. The entire procedure takes only a few minutes, and the sealant remains effective for up to five years. The sealant acts as a barrier between bacteria and tooth enamel, preventing bacteria from degrading the tooth. Sealants are increasingly being used on children's teeth because they can reduce molar cavities by more than 50%, according to the ADA.
Most sealants contain bisphenol-A diglycidyl methacrylate (bis-GMA), a common ingredient in restorative dental materials since the 1960s. Although most of the bis-GMA is polymerized during curing of the sealant, Olea and his colleagues found that unpolymerized monomers of bis-GMA, bisphenol-A and bisphenol-A dimethacrylate, leached into the saliva one hour after treatment. The amount of these compounds in saliva translated to 0.1-2% of the 50 milligrams of sealant applied. Enzymes in the saliva, along with chewing, could contribute to persistent breakdown of bis-GMA, and animal studies have indicated that a significant portion of this material is absorbed by the intestine.
In a written statement, the ADA called the study "interesting," but questioned Not something to smile about? Recent data on dental sealants suggests they may leach estrogenic chemicals into the body.
whether the estrogenic potential of the sealant compounds would survive the acidic environment of the human gastrointestinal tract. "The amount of leachable materials still needs to be quantified," wrote Chris Martin, manager of ADA Media Relations. "The biological implication of this observation needs to be further elucidated. . . The ADA cannot at this time draw definitive conclusions from this [study's] observation." Olea and co-workers report that the amount of bisphenol-A and bisphenol-A dimethacrylate in dental sealants varies depending on the manufacturer and batch. An earlier study of 12 commercial dental resins by Vankerchkhoven and colleagues, published in the Journal ofDental Research in 1981, found bis-GMA in all samples ranging from 19% to 51% of the total weight. The amount of monomer compounds leached from the sealant also depends on the degree of polymerization effected by the curing process. Typically, 60-75% of the material is polymerized, although levels as low as 30% may be found at the bottom of fillings.
In the E-screen test, which is based on the ability of human breast cancer cells to proliferate in the presence of estrogens, cell cultures treated with four different bis-GMA-based sealants proliferated sixfold more than control cultures. The proliferative effect of the sealants was similar to that seen with the natural estrogen estradiol-17&. Bisphenol-A has been shown to be toxic to fish; in mice, it induces photoallergic dermatitis, can be fetotoxic, and affects sperm motility.
"What we know is that it seems to be a significant amount of bisphenol-A being leached from sealants," says Ana Soto, one of the authors of the study. Soto points out that, although the significance of dental sealants in terms of total exposure to xenoestrogens is unknown, "the quantity is enough that we are pursuing it further." American Health Foundation 1996 International Course on the Safety Assessment of Pharmaceuticals The American Health Foundation's 4th International Course on the Safety Assessment of Pharmaceuticals, Part 1, Regulatory Aspects, is designed mainly for scientists of the phgrqmaceutical industry in charge of nonclinical or clinical studies and also for those responsible for the registration of drugs. Participants will receive the scientific information necessary for a sound comprehension of the results of, studies. Toxicologists and toxicologic pathologists will also benefit from this course by updating their kno g rse will be held on October 20-25, 1996, at the Crowne Plaza in the heart of White Plains, New York, just 3 utes north of New York City. For a brochure and registration information, please contact Ms. Nancy Rivera at the American Health Foundation, 1 Dana Road, Valhalla, NY 10595-1599; telephone (914) 789-7144, FAX: (91 4) 592-6317.