back.jpg (3238 bytes)DEPARTMENT OF HEALTH & HUMAN SERVICES
Public Health Service


Food and Drug Administration
Rockville MD 20857

May 5, 1997

The Honorable Edward J. Markey
Ranking Minority Member
Subcommittee on Telecommunications,
Trade, and Consumer Protection
Committee on Commerce
House of Representatives
Washington, D.C. 20515-2107

Dear Mr. Markey:

This is in response to your letter of April 7, 1997, regarding the status of the Food and Drug Administration's (FDA) oversight and investigation of wireless communication health effects.

Little is known about the possible health effects of repeated or long-term exposure to low levels of radiofrequency radiation (RF R) of the types emitted by wireless communications devices. Indeed, much controversy exists within the scientific community regarding the potential for health effects from any type of low-intensity RF R.

RF R extends from approximately a few kilohertz (kHz) to 300 gigahertz (GHz) on the electromagnetic spectrum. Cellular phones emit RF R at a frequency of about 824-915 megahertz (MHz). The new Personal Communications Systems (PCS) emit at 1850-1910 MHz. In addition, radar systems emit in a band of 100 MHz and 100 GHz. Many other consumer products emit in this range, e.g., AM radios around 1 MHz, CB radios at 27 MHz, televisions at 50-500 MHz and above, and microwave ovens at 2450 MHz (2.45 GHz). Each frequency may have unique properties in terms of potential bioeffects and it may not be possible to extrapolate results found at one frequency with those of another.

The Center for Device and Radiological Health's (CDRH) specific involvement with cellular phones began in early 1993 when the issue of brain cancer and its possible association with cellular phone use was raised via a nationally televised interview with a man who attributed his wife's death from brain cancer to her frequent use of a cellular telephone. In early 1993, CDRH requested several meetings with industry to discuss the inadequacy of the data that exists with which to evaluate claims of health risks such as cancer. At the meetings, CDRH presented the need for properly credentialed research, proper labeling, and possible redesigns to address the issues related to potential bioeffects from the radiofrequency energy emitted by hand-held cellular phones. Industry groups represented at the meeting were manufacturers and distributors of cellular phones, communications firms, and related trade associations. In response to an industry request that Federal agencies play a role in directing the necessary research, CDRH offered to explore the possibility of working under a Cooperative Research and Development Agreement. This agreement was ultimately not accepted by the Cellular Telecommunication Industry Association (CTIA) so CDRH's role in the industry program became an advisory one.

The overall industry effort has since evolved to the current program manager by Wireless Technology Research, L.L.C. (WTR), which is funded by industry through a blind trust arrangement. WTR published its research agenda and requests for proposals (RFP) in 1994 and 1995. CDRH discussed detailed comments on the RFP with Dr. George Carlo, Chairman of WTR, and his colleagues from WTR.

As a result of the oversight briefing with the Subcommittee you chaired in February 1993, the Environmental Protection Agency (EPA), together with CDRH, the National Institute for Occupational Safety and Health (NIOSH), the Occupational Safety and Health Administration (OSHA), the Federal Communications Commission (FCC), and the National Telecommunications Information Agency (NTIA) reconstituted a Radiofrequency Inter-Agency Work Group (RFIAWG) in August 1994 to coordinated issues of concern to these agencies, including monitoring RF R from wireless communication. This group has been instrumental in providing a coordinated Federal response to industry's research as recommended in the 1994 GAO Report entitled, "Status of Research on the Safety of Cellular Phones."

WTR met with representatives of the RFIAWG in 1995 and 1996 for the purpose of discussing details of the WTR research plans and progress. In a March 13, 1997 letter (TAB A), CDRH communicated a statement of RFIAWG research priorities to WTR. CDRH solicited input from the RFIAWG in responding to your specific questions.

Most of the studies of RF R in the published literature have investigated the biological effects of exposure to radiofrequency radiation characteristic of radar or microwave ovens. Many of the published studies involve acute exposure of animals or cells in vitro to short, intense RF R doses which do not use the frequencies or modulations used for cellular phones. Cellular phone exposures are at lower RF R doses and, due to frequent cellular phone use, are chronic. Higher does exposures are thought to produce effects as a result of increased temperature. It is not known whether lower doses produce bioeffects through non-thermal mechanisms or whether they produce cumulative effects. We have included a summary of some recent studies in the enclosed Appendix.

QUESTIONS

    1. (a) What type of scientific research is needed to fully assess whether RF exposure from wireless phones pose a health risk to consumers? (b) What research is the WTR conducting? Is this the type of research that is necessary to fully assess whether RF exposure from wireless phones pose a health risk to consumers?

(a) In order to assess whether RF R exposure from wireless phones poses a health risk to consumers, a combination of laboratory studies, and epidemiological studies of human populations actually using cellular phones is needed. Laboratory studies should include engineering and dosimetric (measurement of dosage) studies of the amount of radiation absorbed in the heads and bodies of wireless phone users, including the ways in which this energy deposition is affected by the users' anatomy, objects such as eyeglasses and jewelry, and the design of the phone itself. Bioeffects studies should include the development of in vitro and in vivo exposure systems, and the use of these systems in cellular and short and long-term animal studies to determine mechanisms of action. Both epidemiological studies and continued postmarket surveillance of exposed human populations are critical.

There is wide agreement within the international scientific community regarding the types of research needed to assess whether RF R from cellular phones poses a health risk to consumers. Research needs have been articulated by a number of groups, including the European Commission1 and the World Health Organization (WHO) which established an International EMF Project and held a meeting in November 1996 to review the status of the science on non-thermal levels of RF exposure and to identify research needs in order to make better health risk assessments.

(b) The WTR has developed a research agenda entitled, "Potential Public Health Risks From Wireless Technology: Research Agenda for the Development of Data for Science-Based Decision Making" (Scientific Advisory Group on Cellular Telephone Research, 1994). The agenda proposed a comprehensive risk assessment strategy, including assessment of the existing literature, development of appropriate dosimetry and exposure systems, epidemiology, in vitro genotoxicology, and animal experiments (with short and long-term exposure). A summary of experiments (with short and long-term exposure). A summary of the WTR research agenda prepared by CDRH is provided in TAB B.

Progress to date appears to have been focused on assessing the existing literature, developing the research agenda, working on dosimetry and designs for both in vivo and in vitro exposure systems, and conducting an epidemiology study of overall mortality of 250,000 phone users.

The type of research proposed by WTR should provide part of the answer to the questions of whether RF exposure from wireless phones poses a health risk to consumers. CDRH recently conveyed to Dr. Carlo at WTR ten recommendations of the RFIAWG as to which elements should be pursued in the near term, given WTR's stated lack of resources to pursue the entire research agenda as a comprehensive program (TAB A).

    2. To your knowledge, is the WTR conducting any biomedical research to assess whether the frequencies and power levels utilized by portable wireless cellular phones produce RF exposure that is unsafe to consumers? If so, please provide a description of such research.

To the best of our knowledge, the research conducted by WTR to date falls into the categories of exposure system development and epidemiological studies. In addition, WTR has devoted much effort to an assessment of the existing research data and the planning of a comprehensive program. The WTR program of exposure system development has led to the design exposure systems for use in both animal studies and studies of cultured cells in vitro. WTR's efforts to design exposure systems that will accurately deliver known levels of RF R to animals and cells in vitro is expected to be valuable to the scientific community.

WTR's epidemiological studies of populations using cellular phones is expected to yield potentially valuable human data, but the studies that can address potential long-term effects will require a number of years. We are not currently able to state when the WTR program will lead to conclusive information, but we believe that it will require an ongoing research effort beyond the current five year program.

    3. Is the FDA fully confident that the research being conducted by the WTR has the independence and scientific integrity to assess adequately portable wireless phone safety? In your opinion, can the Federal government, and American consumers, rely on the results of this industry-sponsored research?

As stated, FDA's role in the WTR research program has been in a scientific advisory capacity. The Agency has no information which would lead us to believe that the Federal Government and the American consumers will not be able to rely on the results of the WTR research. The research agenda was subjected to peer review coordinated by the Harvard University School of Public Health Center for Risk Analysis. As with all scientific research, research results also will be expected to undergo the rigors of a scientific peer review as part of the publication process.

    4. What research has been conducted at any Federal agency since 1993 to assess whether the frequencies and power levels utilized by portable wireless phones produce RF exposure that is unsafe to consumers? Please list the agencies, types of research, and expected dates for completion of such research. If no such research has been, or is being conducted, please explain why not.

To the best of our knowledge, there is no current large scale research effort underway by the Federal agency to assess the frequencies and power levels utilized by portable wireless phones. The National Cancer Institute (NCI), however, has included wireless communication use in its comprehensive study of brain tumor associations with environmental factors. The study has been underway since 1994, with reports on the findings expected to appear in the fall of 1999. The cost of the entire study is approximately $2.2 million, but it is not possible to ascertain separately the cost of the component focusing on cellular phone use. In addition, CDRH has performed both experimental and computational investigations of the energy deposition in the body from cellular phones. Finally, NIOSH has conducted RF R research involving laboratory studies, instrumentation development, and field studies. This research, however, has concentrated on equipment and situations where the strongest occupational exposures to RF R are known to occur, i.e., with workers using RF heaters and other industrial equipment, and maintenance workers of broadcast RF antennas. NIOSH has not conducted any studies specifically addressing the health effects of cellular telephone use.

To address the possible health effects of non-ionizing radiation, Federal agencies have focused research on studies of possible bioeffects of electric and magnetic fields associated with generation, transmission, distribution, and use of electric power. Such research has been given priority over RF R health effects research, in part, because of the Congressional appropriations and research mandate of the Energy Policy Act of 1992.

    5. Has the Federal government sponsored or funded any outside research since 1993 that specifically analyzes whether the frequencies and power levels utilized by portable wireless phone produce RF exposure that is unsafe to consumers? Please list the organization conducting such research, the amount of Federal support, and the expected dates for completion of such research. If no such research has been, or is being conducted or funded, please explain why not.

To the best of our knowledge, there is no Federal Government sponsored research specifically directed toward cellular phone safety. EPA is sponsoring a study by the National Council on Radiation Production and Measurement (NCRP) on the impact of signal modulation on the effective RF R dose delivered to tissue. The NCRP study, started in 1995 and expected to be completed in 1997, is funded at a level of $100,00 by EPA's Office of Radiation and Indoor Air. Although not directed specifically toward cellular phone safety, the information developed by this study is expected to be useful in several facets of RF R research, including wireless communications. This study is necessary to help determine, for instance, whether the exposures from digital phones are biologically equivalent to those from analog phones with the same time-averaged energy deposition.

In addition, we understand that the Department of Defense conducts research on basis bioeffects. A small portion of this program is devoted to studies of low powered exposures with relevance to cellular telephones.

    6. Since 1993, has the Federal government conducted any research itself, received any research data from the WTR, or received any outside research results, that serve to reassure the public that portable wireless phones are safe? If so, please describe such research.

To the best of our knowledge, there have been no definitive research results since 1993 that can serve to completely reassure the public that portable wireless phone are safe. As noted in the Appendix, Rothman et al. (Rothman, et al. 1996. Epidemiology; 7:303-305) conducted an epidemiological study, that was sponsored by WTR and published in 1996, of more than 250,000 portable and mobile telephone users. Overall mortality rates of cellular phone users were reported to be less than that of the corresponding rates for the general population, a finding that may be related to the socioeconomic status of cellular phone users. No significant difference was observed in the mortality rate ratio for portable vs. mobile cellular phone users. Users of hand-held cellular phones have a higher exposure to RF R than do users of mobile cellular phones. As a general rule, there is a relatively long latency period between exposure to a carcinogen and the diagnosis of a tumor, e.g., asbestos exposure and mesothelioma. In the Rothman study, the period between exposure to cellular phones and the ascertainment of mortality of study participants was relatively brief, and less than the latency period of many carcinogens. Therefore, the Rothman study does not rule out the possibility of a long-term relationship between cellular phones and cancer. Continued follow-up of the study participants is warranted. The possible relationship between cellular phone use and specific causes of mortality, such as brain cancer, also was not addressed by the study.

Another study, which has not been published but which has been presented at the June 9-14, 1996 Bioelectromagnetics Society meeting, was conducted for Motorola by Dr. Ross Adey at the Jerry L. Pettis Veterans Administration Hospital and involved lifetime exposure of rats to cellular phone RF R (see Appendix).

    7. Since 1993, has the Federal government conducted any research itself, received any research data from the WTR, or received any outside research results, that serve to diminish confidence that portable wireless phones are safe? If so, please describe such research.

To the best of our knowledge, there have been no definitive research results since 1993 that serve to diminish confidence that portable wireless phones are safe. The Lai-Singh study (see Appendix) has generated considerable scientific interest among RF R bioeffects researchers, and is often cited as evidence of potentially adverse effects of RF R exposure.

    8. When does the FDA expect to be able to make any conclusive statements about health risks associated with RF exposure from portable wireless phone use?

It is difficult to predict when conclusive statements about health risks can be made. If we rely on epidemiological studies alone, data may not be available for many years because there is a relatively long latency period between exposure to a carcinogen and the diagnosis of a tumor. Earlier, indirect evidence on risks can be obtained through animal and cellular studies. This illustrates why the best approach includes both epidemiological and experimental studies. It is encouraging to note that this subject is receiving world-wide research attention.

In summary, there is currently no specific information that clearly indicates that use of cellular phones is a human health risk. On the other hand, there is not enough information available to permit a determination that there is no health risk. A significant research effort, involving exposures of large numbers of animals to the various types of cellular phone modulation in current on expected use, coupled with epidemiological surveillance of exposed populations, is needed to provide a further basis for risk assessment of these devices.

In closing, let us assure you that FDA has a long-standing commitment to protecting the public health from hazards associated with radiation-emitting products. If we may be of any further assistance, please let us know.

Sincerely,



Diane E. Thompson
Associate Commissioner
for Legislative Affairs

Enclosures



APPENDIX

Repacholi, et al. 1997. Radiation Research, pp. 631-640.
A study in the May 1997 issue of the journal Radiation Research reported an increased incidence of lymphoma in mice exposed to the type of RF R emitted by digital cellular phones. In this study, mice that had been genetically engineered to carry a cancer-causing gene were exposed to the RF R for 30 minutes twice a day for up to 18 months. A control group of mice with the same gene were housed and treated in the same way but not exposed to the RF R. In the mice exposed to the RF R, the incidence of cancer of the lymphoid system increased from 22% to 43%.

This study makes an important contribution in the area of wireless technology research. However, the mouse assay system used is not well-characterized with respect to its ability to predict carcinogenesis so the results are not extrapolatable to humans, or even to normal mice. Moreover, the results of any single experiment need to be confirmed by repetition in other laboratories before it can be concluded that the results are reliable. In addition, the mice were exposed toe RF R under conditions that may not simulate the type of exposure humans receive. Finally, the type of RF R used in the experiment is the kind emitted by digital cellular phones in Australia. Most cellular phones used in the United States are analog phones so the applicability of this study to American cellular phone users is unknown.

Chou, et al. 1992. Bioelectromagnetics, 13:469-496.
A frequently cited study was conducted in the early 1980s at the University of Washington for the United States Air Force and is usually referred to as the Guy study. Two groups of 100 rats were used in the study, with one group being exposed to RF R for 22 hours each day for approximately two years. The other group of rats was an unexposed control group. The frequency and modulation of the RF R was different from that used in cellular phones, but the energy deposited in the rats' bodies was similar to the maximum doses in the heads of cellular phone users. Eighteen rats in the exposed group developed tumors, while only five rats in the control group developed tumors. The difference is statistically significant, but the study has never been replicated and it is possible that the results were due to some factor other than RF R exposure.

Adey, et al. June 9-14, 1996. Proceedings of the Eighteenth Annual Meeting of the Bioelectromagnetics Society, pp. 27.
In a more recent study conducted for Motorola at the Veterans Administration Hospital in Loma Linda, California, rats were exposed to a chemical carcinogen that causes brain tumors and then to an actual cellular phone RF R source. There were slightly fewer brain tumors in the exposed group, but the numbers of animals that developed tumors was not large enough to support a finding that cellular phone RF R protects against tumors. Dr. Adey has reported the experiment at scientific meetings and said it is being repeated with a larger numbers of rats.

Lai and Singh. 1996. Int. J. Radiat. Biol., 69:513:521.
Another recent study, referred to as the Lai-Singh study, has also aroused considerable interest. In this study rats were exposed for two hours to RF R levels comparable to those received by cellular phone users, though the frequency and modulation of the RF R was different from actual cellular phones. Using a novel technique, the investigators studied cells isolated from the rats' brains and found that rats exposed to RF R has an increased number of DNA strand breaks relative to the unexposed controls. Some scientists have interpreted these results as suggesting a possible mechanism whereby RF R might influence tumor development, but this experiment does not clearly indicate a health hazard. The utility of this assay for genotoxicity testing is currently a subject of interest and investigation.

Kues, et al. 1992. Bioelectromagnetics, 13(5):379-393.
Cataract is an established bioeffect and thought to be a thermal effect. The blood-aqueous barrier in the eye and effects on the retina have been investigated by Kues and coworkers at Johns Hpokins. They found an increase in blood-aqueous barrier permeability at 2450 MHZ. Most existing data suggests that direct genotoxic effects of RF R are unlikely, however (note the Lai-Singh report above).

The Institute for Working Life
More recently, there has been interest in effects reported/studied in humans. When some factory workers in Sweden switched from analog to digital cellular phones at work, they reported headaches which apparently went away when they resumed using analog phones. The Institute for Working Life in Sweden is conducting a study examining self reports of headaches and other symptoms as endpoints; however, this type of study is fraught with difficulty given the subjective nature of the symptoms used as endpoints.

Rothman, et al. 1996. Epidemiology, 7:303-305.
Kenneth Rotham published an epidemiological study, sponsored by WTR, that failed to find an adverse effect on the short-term mortality of cellular phone users. A detailed discussion of this study is provided in the response to question 6.

National Cancer Institute
The National Cancer Institute is including cellular phone use as a variable in a current study of brain cancer.




TAB A

DEPARTMENT OF HEALTH & HUMAN SERVICES
Public Health Services


Food and Drug Administration
9200 Corporate Boulevard
Rockville MD 20850


March 13, 1997

George L. Carlo, Ph.D., M.S., J.D.
Chairman
Wireless Technologies Research, L.L.C.
1711 N Street, N.W.
Suite 400
Washington, DC 20036-2811

Dear Dr. Carlo:

As the lead federal agency charged with regulation of radiation-emitting consumer products, the Food and Drug Administration (FDA) has followed the progress of your research effort into the possible health effects of wireless technology with great interest. We are continuing to work with the other members of the Radiofrequency Inter-Agency Work Group in order to provide a coordinated set of comments on your program, as was recommended by the U.S. General Accounting Office in their 1994 report to the Chairman of the House Subcommittee on Telecommunications and Finance, Committee on Energy and Commerce. We were pleased that we could participate in your Cellular Telephone Research and Cancer Symposium held in December 1993, and we benefited greatly from the informative briefings you delivered to the Inter-Agency Work Group in March 1995 and August 1996. We are also pleased to give you the suggestions of the Inter-Agency Work Group regarding priorities for the directions your research should take, as you and the Cellular Telecommunications Industry Association have requested. A number of these suggestions have been voiced at our meeting with you, but we would like to take this opportunity to reiterate them here.

Our suggestions for research priorities should in no way be construed as a rank ordering of priorities; we simply wish to state some of our views of what a well-balanced program of research should look like. As was noted in the proceedings of your 1993 symposium, "A balance seems best between epidemiological studies, animal studies, and mechanistic studies, even if the last category cannot be extrapolated". Since your resources are limited, we will attempt to offer our views on how your program could be redirected in order to best answer the questions that the regulatory agencies believe are relevant to out concerns.

As it is currently planned, the Wireless Technologies Research, L.L.C. (WTR) research program consists of five elements: dosimetry and exposure system issues, epidemiology, in vitro genotoxicology, and rodent bioassays, both chronic and subchronic. We would like to offer the following points that we believe should be considered in deciding, which of these elements to pursue in the near term, given the lack of resources to pursue them as a comprehensive program:

  • Chronic (lifetime) animal exposures should be given highest priority.
  • Chronic animal exposures should be performed both with and without the application of chemical initiating agents to investigate tumor promotion in addition to tumorigenesis.
  • Identification of potential risks should include endpoints other than brain cancer (e.g., ocular effects of radiofrequency radiation exposure).
  • Replication of prior studies demonstrating positive biological effects work is needed. A careful replication of the Chou and Guy study (Bioelectromagnetics 13:469-496, 1992) which suggests that chronic exposure of rats to microwaves is associated with an increase in tumors would contribute a great deal to the risk identification process for wireless communication products.
  • Genetic toxicology studies should focus on single cell gel studies of DNA strand breakage and on induction of micronuclei. (These are the only direct genetoxic effects suggested at this time.) The need to replicate the Lai and Singh experiments used to demonstrate microwave-induced DNA strand breakage (Int. J. Radiat. Biol. 69:513-521, 1996) is strengthened by Dr. Lai's recent reports in scientific meetings that this effort is suppressed by melatonin exposure.
  • Epidemiology studies focused on approaches optimized for hazard identification are warranted (e.g., case control studies are well suited to studying rare diseases such as brain cancer).

Due to the latency of some of the health effects that have been suggested to be associated with exposure to non-ionizing radiation, long term study is essential to test such associations. Indeed, we believe that continuing postmarketing surveillance is important in ensuring the safety of wireless technologies.

We believe that products of the WTR research program could have lasting benefit to any organization that may conduct research on the possible health effects of exposure to radiation from wireless communications devices. We hope that WTR finds these suggestions helpful as you enter the implementation stage of your biological research. If we can be of further assistance, please don't hesitate to contact me.

Sincerely yours,



Elizabeth D. Jacobson, Ph.D.
Deputy Director for Science
Center for Devices and
Radiological Health




TAB B

Wireless Technology Research, L.L.C. Research Agenda Overview

Among the initial functions of WTR were to collect, review, and assess available research on the potential effects of RF R, define the areas for which information is needed, and develop a research plan. The resulting research agenda required 15 months to develop, including a seven month review period. The research agenda was subjected to peer review of a Peer Review Board coordinated by the Harvard University School of Public Health Center for Risk Analysis. The risk evaluation research program encompasses a tiered approach to both developing information and placing appropriate weight on specific scientific findings.

Tier I studies involve the development of RF R exposure systems relevant to wireless communication instruments, including cellular phones and conduct of toxicology studies in accordance with standard approaches to product safety evaluation. Tier II studies encompass epidemiological evaluations and longitudinal surveillance of cellular telephone users, employing appropriate measures of real life exposures. Tier III studies will address mechanistic issues arising from studies conducted under Tiers I and II which are suggestive of a public health risk. These will consist of in vitro or in vivo mechanistic studies conducted as needed to assist in the interpretation of results from Tier I and Tier II studies.

The goal of the Tier I exposure system development is the development of exposure systems for both in vivo and in vitro experiments that appropriately represent actual human exposure conditions and that are, to the degree possible, standardized across investigations. In particular, WTR has decided to develop in vivo exposure systems which produce ratios of head to whole body exposures that are typical of actual human exposures, rather than the more traditional whole body exposures. WTR is coordinating this effort through its Dosimetry Working Group. WTR has chosen to use a single-site facility for all in vitro studies in order to assure consistency across all in vitro studies, as well as to reduce costs associated with facility construction and operation.

The central focus of the Tier I toxicology research program is the assessment of potential carcinogenicity of RF R exposure, using the same research paradigm as commonly used for regulatory assessment of the safety of chemical agents. The tests will involve standardized short-term tests for genotoxicity and various long-term animal studies. After learning of Dr. Lai's results suggesting the genotoxicity of RF R in rats' brains, WTR convened an expert panel to review these results and stated that they would repeat this experiment under exposure conditions relevant to human cellular phone exposures. The genotoxicity studies planned by WTR include standard in vitro microbial and mammalian cell mutation assays and a chromosomal aberrations assay using human lymphocytes. The WTR in vivo toxicology program will focus on the collection of information needed to design long-term animal bioassays by first initiating subchronic animal exposure studies, with emphasis placed on the evaluation of signs of tissue-specific toxicity. WTR has concluded that animal tumor promotion studies should not be used for human health risk assessment until there is clear evidence of a casual relationship between RF R and biological effects related to tumor promotion.

The Tier II epidemiology studies planned and being undertaken by WTR focus on the following types of malignancies: gliomas, meningiomas, nerve sheath tumors (including acoustic neuromas), parotid gland tumors, and adult-onset leukemia. WTR has stated that it will focus on investigations involving both cohort and case-control studies. Cohort studies will be used to assess general mortality and morbidity of cellular phone users, while case-control studies will focus on the specific types of tumors listed above. WTR plans to investigate the potential to use the telephone companies' billing logs to provide a surrogate measure of RF R exposure. They will then link this exposure data with specific outcome databases in order to evaluate relevant causes of morbidity and mortality among the cohort.

Tier III studies will be planned as part of the evaluation of the data to be obtained from the Tier I and Tier II stuides.

Summary prepared by the Center for Devices and Radiological Health

1 "Possible Health Effects Related to the Use of Radiotelephones; Proposals for a Research Program by a European Commission Expert Group," Oct. 1996, A.F. McKinley, editor [available on request to the European Commission, DG XIII.A.1 (fax + 32-2-296 83 91) and on the Commission's ISPO site on the Internet]

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