National Researh Council Weighs in on Transgenic Plants.

Farmers have been trying to minimize their losses from crop pests for hundreds of years by using conventional breeding practices, such as hybridization, to develop crops with desirable traits. Some types of worms cause an estimated $7 billion in crop losses per year in the United States; the damage from insects is even more severe. In the past two decades, scientists have used advanced knowledge of molecular biology to more precisely alter plants. The new methods introduce genes that endow plants with pesticidal traits, creating what are known as transgenic pest-protected plants. These genes may come from similar, sexually compatible species or from completely unrelated organisms. Transgenic plants have been grown commercially since 1995, and their use has increased dramatically since then. In 1999 alone, more than 70 million acres of transgeuic crops were planted in the United States.

But some scientists and members of the public have expressed concern that the genetic engineering of plants could result in unsafe foods, do irreparable harm to beneficial organisms, and spur the uncontrollable growth of weeds. Given the dramatic increase in commercial planting of genetically engineered crops and the safety concerns they raise, the National Research Council decided to review the scientific data on health and environmental risks and the use of these data in the regulatory process.

Health-Related Concerns

Thus far, pest-protected plants have caused obvious health or environmental problems only under rare circumstances. For example, although a human allergic reaction to a new gene product has never been documented for a commercially available transgenic pest-protected plant, one such incident did occur at the research stage. In that study, people with a known allergic reaction to Brazil nuts experienced a similar reaction when they were exposed in skin-prick tests to soybeans containing a gene transferred from the Brazil nut.

Priority should be given to developing improved methods for identifying potential allergens, specifically focusing on new tests relevant to the human immune system and on more reliable animal models, according to a report from the National Research Council (NRC). Changes in plant physiology and biochemistry should be monitored during the development of pest-protected plants. Also, because transgenic plants potentially could have increased levels of toxic plant compounds, the U.S. Environmental Protection Agency (U.S. EPA), the U.S. Department of Agriculture (USDA), and the Food and Drug Administration (FDA) should create a coordinated database that lists information about natural plant compounds of dietary or toxicological concern. That database would aid researchers who monitor concentrations of these compounds in genetically modified plants.

Environmental Concerns

In examining ecological concerns, the committee that wrote the NRC report looked at the possibility that transgenic plants could affect organisms that are not the target of the pesticidal trait. The committee also considered the potential transfer of novel genes from one type of plant to another and the evolution of new strains of immune pests.

Both conventional and transgenic pest-protected crops could affect nontarget species, such as beneficial insects, but that impact is likely to be smaller than the impact of chemical pesticides, the committee said. In fact, when used in place of chemical pesticides, pest-protected crops could lead to greater biodiversity in some geographical areas. The committee called for more research to examine these issues.

The highly publicized report of monarch butterflies being poisoned by pollen from genetically engineered corn is an example of an issue that needs to be researched further and will require rigorous field evaluations, the committee said. Pollen from corn that had been genetically engineered to produce Bacillus thuringiensis (Bt) toxin--a type of insecticide--was shown to slow the growth and sometimes to kill monarch caterpillars when enough pollen was placed on milkweed leaves fed to them in a laboratory Follow-up studies are needed in the field, where pollen density might be lower and the toxin might be deactivated by environmental factors.

Another source of concern is the possibility that genes for pest resistance might be exchanged among cultivated crops and their weedy relatives, potentially exacerbating weed problems. The committee recommended further research to identify plants with weedy relatives, to assess rates at which pest-resistance genes might spread, and to develop techniques for decreasing the likelihood of such transfers.

The potential for pests to evolve and develop a resistance to genetically modified plants also raises concern. The committee concluded that the ability of pests to adapt and develop resistance should continue to be evaluated. Such an occurrence could have a number of potential environmental and health consequences, including a return to the use of more harmful chemical pesticides. Strategies to manage the development of resistance in pests should be encouraged for all kinds of pesticides, whether they occur in spray form or are produced by a plant.

Improving the Regulatory Framework

The NRC report argues that to improve coordination, U.S. EPA, USDA, and FDA should develop a memorandum of understanding for regulating transgenic pest-protected plants. The memorandum should identify regulatory issues within the purview of each agency as well as issues for which more than one agency has responsibility. It also should establish a process for ensuring appropriate and timely exchange of information between agencies. For 14 years, the agencies have formulated policies for genetically modified foods under guidelines set forth in the 1986 Coordinated Framework for the Regulation of Biotechnology. That framework gave each agency a role in setting safety standards based on legal jurisdictions at the time. Nevertheless, the scope of each agency's oversight needs to be clarified, especially when a new product is to be reviewed by more than one agency.

The committee took issue with exemptions in U.S. EPA's 1994 proposed rule for regulating certain transgenic pest-protected plants. U.S. EPA proposes to grant categorical exemptions for all plants that have been given a new gene from a sexually compatible plant, as well as for all plants expressing proteins that are derived from a virus (viral-coat proteins). The NRC report points out that the transfer and manipulation of genes between sexually compatible plants could in some cases increase human and environmental exposure to high levels of toxins. Also, while it may be safe to eat plants with viral-coat proteins, environmental issues should be considered because of the potential for crossbreeding with weedy relatives. The committee urged U.S. EPA to reconsider its plans to grant categorical exemptions for these transgenic plants.

The committee also recommends that U.S. EPA, USDA, and FDA monitor the ecological impacts of pest-protected crops on a longterm basis. Monitoring would ensure the detection of problems that may not have been predicted from tests conducted during the registration and approval process.

Finally, the report says, a more open and accessible regulatory process is needed to aid the public in understanding the benefits and risks associated with transgenic pest-protected plants. To increase access to the process, existing Web sites associated with the coordinated framework should be expanded to include more detailed information and to provide links to the decisions all agencies have made for any particular product.

Copies of Genetically Modified Pest-Protected Plants: Science and Regulation are available from the National Academy Press at [phone] or [phone]. The cost of the report is $50 plus shipping charges of $4.50 for the first copy and $0.95 for each additional copy