FY 2000 Medical Uses Of And Environmental Exposures To Radiation
- Optimization of Accelerator Targets for Neutron Capture Therapy
- In vitro Biological Effects of Wireless Telephone Emissions
- Parameters for Testing and Standardization of Skin Types and Skin Response to UV
- Laboratory support for a revised risk assessment of skin cancer from UV-emitting devices
- Biological Effects of Exposure to Electromagnetic Fields
- Sunlamps and Sunbeds: Activities related to possible amendments to the Performance Standard for Sunlamp Products
This program encompasses a collection of biological research projects needed to ensure that the public enjoys the benefits of modern medical and consumer technology without undue harm due to associated radiation exposures. Another goal of the program is to prevent unnecessary exposure of the population to radiation emitted from electronic products and to establish the scientific basis for regulatory decisions involving electronic product radiation.
Boron Neutron Capture Therapy (BNCT) promises the potential of becoming a major new modality for the treatment of brain tumors, whose therapy is currently problematic. Its clinical investigation and commercialization will raise a number of new medical device and drug-device issues for CDRH and CDER. OST has worked toward developing computational capabilities to verify dosimetric data submitted in IDEs and PMAs. One of the current challenges to bringing BNCT to the clinic is the design of epithermal neutron beams which will result in safer and more effective therapy by maximizing tumor dose while minimizing normal tissue dose. Since reactor neutron sources are unsuitable for siting in hospitals, there is a need for computational design of beam generators employing particle accelerators. This requires extensive modeling of combinations of charged particle neutron sources, moderators, and reflectors to optimize the dose delivered to a tumor mass. Variables to be considered include tumor dose for various tissue depths and dose to normal tissues from boron capture, as well as proton recoil and nitrogen capture reactions and capturing gamma rays from the target structure. These calculations will provide guidance on desirable properties of neutron beams proposed for IDE's and can serve as a basis for the design of a future experimental facility. Until recently, powerful neutron sources were limited to a very few locations at existing nuclear reactors and thus not generally available for patient treatment. The marketing of a new generation of powerful nuclear particle accelerators, comparable in price to the accelerators currently used for radiation therapy, will soon make clinically useful neutron sources available for therapeutic applications.
Currently over 100 million Americans use wireless phones. This exposure of large numbers of people to radio frequency radiation (RFR) is unprecedented. Data relating to the safety of wireless phones is currently inadequate to determine whether adverse health effects are likely to result from these exposures. A small number of chronic rodent exposures have been conducted which show no evidence of cancer in exposed animals; but one of these studies did indicate an increased number of lymphomas in susceptible transgenic mice. In addition, in vitro studies have been reported to show changes in enzyme activity that are suggestive of cancer-promoting effects. Another in vitro study showed an increase in micronucleus formation, a possible marker for epigenetic effects on DNA synthesis, in human cells exposed to wireless phone emissions. Research into the bio-effects and effects on medical electronics of cell phone use continues. OST developed and established a cooperative research agreement allowing FDA to better assess the possible health risks associated with mobile phone technology. Once the mobile phone industry has initiated this research, FDA will provide ongoing scientific and technical oversight of the research programs. OST research investigated some of the reported in vitro effects using an exposure system calibrated in terms of specific absorption rate. This research, along with extensive involvement in research with other laboratories, aids assessing published data that suggest the biological effects of exposure to radio frequency radiation at levels relevant to wireless phone use.
OST studies of the utility of novel noninvasive and biomarker methods to test and standardize skin responses to ultraviolet radiation (UV) can provide data needed for revising the national and international standards in the area. Such research supports CDRH policies for ultraviolet lamps used in medicine and cosmetology, CDER policies related to sunscreens and photosensitizing drugs, and CFSAN policies in the area of cosmetics. FDA’s policies regarding sunlamps has been repeatedly questioned by the consumers, the industry, and the medical community. OST research will include the collection of data on human subjects representing skin types I-VI and racial ethnic groups of (1) American Indians or Alaska Natives, (2) Black or African Americans, (3) Asians, (4) Hispanic or Latinos, (5) Native Hawaiians or Other Pacific Islanders, and (6) Whites. These data include changes in the skin properties following UV exposure assessed using two mechanical methods, four optical methods, one ultrasound method, and several biomarkers measured in the biopsies. OST data provide a solid scientific basis for improving the classification and testing of human skin sensitivity to UV.
Some UV-exposed skin cells do not die. Rather they acquire genetic mutations that can lead to skin cancer. Inhibition or failure of cells to die when too many genetic mutations have been acquired has recently been implicated as a mechanism for initiation and promotion of skin cancer by UV. In vitro laboratory data from cell exposure to UVA and UVB wavelengths separately, which are both emitted to different degrees from tanning lamps and, together, can be used to establish adjustments that should be made to existing UV risk assessment equations. Until recently, no risk assessment of tanning lamps for skin cancer could be accurately performed because only the action spectrum, i.e., data for the individual UV wavelengths, was known. The combined output effect on skin cancer from tanning lamps, i.e., UVA and UVB wavelengths, could not be established because a definitive biological endpoint to monitor in human cells was not established. OST data can be used to see if an additive, synergistic, or antagonistic effect occurs when UVA and UVB are combined together, as they are in tanning device emission. With this data, scientists will be able to complete a risk assessment because they will know the appropriate approach and equations to use in this tanning lamp situation.
Radiation scientists are assessing the utility of several testing methods for charcterizing the effects of UV radiation on skin for potential use in the regulation of products such as sunlamps, tanning booths, sunscrenns, and photosensitizing drugs. In addition, a cross agency effort to estimate the effect of exposure to ultraviolet radiation and implement efforts to reduce exposures. The studies, initially funded by grants from the FDA Office of Science have begun to yield results that are useful in developing standards for determining UV exposures and for validating predictive models of tissue behavior when exposed to UV.
The projects described below are complimented by standards development activities, particularly in the areas of nonionizing radiation exposures. The OST scientists responsible for this research are active in the revision of international standards and guidelines for ultraviolet, radio frequency, and extremely low frequency radiation.
Optimization of Accelerator Targets for Neutron Capture Therapy
Key words: cancer therapy, boron, neutrons
Boron Neutron Capture Therapy (BNCT) remains a promising investigational therapy for brain tumors, and it uses boron-10 and a neutron beam to selectively produce highly ionizing helium nuclei (alpha particles) in a tumor while only producing minimal damage to the surrounding brain tissue. A variant of BNCT, capture synovectomy, has been proposed and patented for ablation of pathological synovium in rheumatoid arthritis refractory to medical treatment. Since there is currently inadequate information about the optimal performance characteristics of devices that would be used to deliver these therapeutic neutron beams, OST has initiated a project to investigate issues of potential regulatory significance using computational modeling. OST developed a computational model of the moderator which must be placed in a fast neutron beam to slow the neutrons to therapeutic energies. Moderators of deuterium oxide, carbon, Teflon, aluminum oxide, lithium fluoride, iron fluoride and an aluminum-aluminum fluoride composite were modeled. The neutron source was a lithium accelerator target bombarded by 2.5 MeV protons. Comparisons of the computed spectra of neutrons emerging from the moderators indicates that aluminum oxide, a cheap and readily available material, gave the highest fraction of epithermal neutrons and lowest contamination by fast and thermal neutrons. OST also collaborated with a local accelerator facility that will allow experimental confirmation of these results as well as in vitro studies of lethality for brain tumor cells.
In vitro Biological Effects of Wireless Telephone Emissions
Key words: wireless communications, cancer
Due to the continuing interest in possible adverse health effects in wireless phone users, OST developed an exposure system utilizing radio frequency (RF) radiation from wireless phones to permit investigation of some of the reported in vitro effects of this radiation. A series of experiments was conducted to calibrate the RF exposure system for exposure of cultured cells to radiation emitted from wireless phones and to characterize the effects of this radiation on the enzyme ornithine decarboxylase (ODC). Precision calorimetry was used to measure the amount of RF energy deposited in cultured cells for both analog and digital phone signals. Experiments were then conducted to verify reports that wireless phone radiation increased the activity of ODC, a marker for tumor promotion, in cells. Exposure to a wide range of RF power levels from wireless phones did not increase ODC activity, although at higher power levels a decrease in activity was observed. This decrease was demonstrated to be due to heating of the cells by the RF radiation. These results are consistent with a large number of experiments conducted by OST, which did not confirm reports from other laboratories that electromagnetic fields enhance ODC activity in mammalian cells and avian embryos.
Parameters for Testing and Standardization of Skin Types and Skin Response to UV
Key words: skin, ultraviolet, UV, sunlamp
Human skin can be damaged by ultraviolet radiation (UV) from the sun, sunlamps, and medical devices. To improve public health policies in this area, FDA is actively involved in revising or developing several national and international standards. However, the current knowledge provides an inadequate scientific basis for such standards, guidelines, and policies.
At present, UV sensitivity is predicted from predisposition to sunburn and tan. Unfortunately, in many cases such predictions fail. This study is being done (in collaboration with the National Cancer Institute) to see if human sensitivity to UV can be objectively predicted using instruments and biological methods. The volunteers (110) are grouped on the basis of their skin type and racial/ethnic origin (OMB 0990-0208: American Indian or Alaska Native; Black or African American; Asian; Hispanic or Latino; Native Hawaiian or Other Pacific Islander; White.) Small areas of the skin are exposed to different UV doses. Then, at different times, instrumental measurements and biopsies are performed.
At this time, the data have been collected on 55 subjects. The results obtained following a single UV exposure show that mechanical methods can detect trends but have no predictive value. An ultrasound technique detects UV-induced changes in the structure of the skin. Optical and biological (analyses of biopsies) methods show high sensitivity and should help to modernize public health policies in the area. Such policies would help consumers to protect themselves from skin cancers and premature skin aging.
Laboratory support for a revised risk assessment of skin cancer from UV-emitting devices
Key words: skin, ultraviolet, UV, cancer, risk assessment
UV research examines the biochemical changes to skin cells and has calculated the annual and seasonal UV doses of American women and men required for relative risk assessments of UV-related health effects. This combined UV research effort allows proper usage and accurate standardization of cosmetic (tanning) and medical phototherapeutic devices. This research also allows science-based risk assessments of UV-induced skin cancers, such as the potentially fatal melanoma, caused by exposure to UV-emitting devices. Expertise supports the Center Offices OC and ODE on risk-benefit issues related to cosmetic and medical devices, such as tanning, phototherapeutic, and other UV-emitting devices (e.g., Halogen and dental lamps).
Biological Effects of Exposure to Electromagnetic Fields
Key words: CRADA, radio frequency, RF, micronucleus
In addition to the intramural research described above, OST is working with the National Toxicology Program to ensure that the need for long-term animal studies is addressed. OST also established a Cooperative Research and Development Agreement (CRADA) with the Cellular Telecommunications and Internet Association (CTIA) to provide research recommendations and research oversight for CTIA-funded studies into the health effects of radio frequency (RF) emissions from wireless phones. OST organized a meeting to obtain broad expert input and issued a detailed description of research needed to investigate the reported ability of wireless phone RF to induce the formation of micronuclei in human blood. Micronucleus formation is an indicator of effects that may be related to carcinogenesis or tumor promotion. CTIA issued a request for proposals to perform the research specified by OST.
Sunlamps and Sunbeds: Activities related to possible amendments to the Performance Standard for Sunlamp Products
Key words: performance standard, sunlamp
FDA presented five possible amendments to its Performance Standard for Sunlamp Products to TEPRSSC on June 21, 2000. The proposed changes included 1) incorporation of an exposure schedule into the Performance Standard, 2) use of a skin cancer action spectrum to determine a recommended yearly maximum exposure to ultraviolet radiation, 3) revised warning labels, 4) clarification of a manufacturer’s responsibilities, and 5) requirement to place warning labels in catalogues, specification sheets and brochure. TEPRSSC requested that FDA meet with the indoor tanning industry to clarify misunderstandings about these possible amendments. That industry-FDA meeting occurred on September 13, 2000. FDA continues to work on a re-draft of its possible amendments.