TY - JOUR
AU1 - Balter,, Stephen
AB - Abstract An incomplete understanding of risk can cause inappropriate fear. Personal protective equipment (PPE) offered for the prevention of brain cancer in interventional fluoroscopists (IR-PPE). Similar items are offered for cell-phone use (RF-PPE). Publications on fluoroscopy staff brain cancer and similar papers on cell-phone induced brain cancer were reviewed. An internet safety product search was performed, which resulted in many tens of thousands of hits. Vendor claims for either ionizing radiation or radio frequency products seldom addressed the magnitude of the risk. Individuals and institutions can buy a wide variety of safety goods. Any purchase of radioprotective equipment reduces the funds available to mitigate other safety risks. The estimated cost of averting an actuarial fatal brain cancer appears to be in the order of magnitude $10 000 000–$100 000 000. Unwarranted radiation fears should not drive the radiation protection system to the point of decreasing overall safety. INTRODUCTION Reducing any health risk usually requires the expenditure of both time and money. Basic safety measures reduce risk at reasonable cost. However, the cost of avoiding an additional injury increases rapidly as the risk of any specific injury decreases. At some point, overall safety is improved by diverting resources away from radiation and toward mitigating other risks. The reasonableness of a safety measure can be quantified in terms of the amount of money needed to avert a statistical death. Highway safety is a good example of safety cost analysis. The number and cause of casualties resulting from highway accidents is directly measurable. Safety can be measured by analyzing traffic statistics. Traffic safety expenditures (~$10 000 000 per death avoided) are substantially higher than legal system awards (~$1 000 000 for an actual death). Part of the safety premium can be attributed to the social value of fear mitigation. Most individuals have little understanding of the magnitude of their risk, and essentially no knowledge of the economics of risk management. Their unfamiliarity often causes unnecessary fear and an overreaction in the quest for the impossible level of perfect safety. Fear and risk avoidance are parts of the human condition. Thus, it is not uncommon to observe the use of fear as a tool in professional communications as well as in the commercial marketplace. Most original epidemiological case studies report the numbers of observed injuries, make assessments of the at-risk population, attempt to attribute a cause and estimate the uncertainty and statistical significance of the findings. Often secondary descriptions of an original study or follow-on scientific papers ‘simplify’ the report by omitting the caveats and leave the impression of absolute certainty. A vendor stays in business by responding to market needs. Sales volume is often increased when products are promoted using simplified reports or forms of misinformation. These activities by themselves tend to increase public anxiety. METHODS AND MATERIALS This paper examines one pair of concrete examples: personal protective equipment (PPE) offered for the prevention of brain cancer in interventional fluoroscopists that might be caused by exposure to scattered radiation (IR-PPE), and PPE offered for the prevention of brain cancer associated with cell-phone use (RF-PPE). Current publications relating to fluoroscopy staff brain cancer and its mitigation and similar papers relating to the risk of brain cancer attributable to cell-phone use were reviewed. The papers appearing in the peer reviewed literature provided a reasonable balance. However, many of these were sensationalized when secondarily reported by newsletters and similar media. Unfortunately, almost all of the ‘common knowledge’ shared by the community is derived from these secondary sources. The availability of ionizing radiation and radiofrequency safety materials was sampled in an internet search that was performed on February 2016 using combinations of relevant search terms. The terms and their overall results are shown in Table 1. The two order of magnitude increase in the number of radiofrequency hits relative to the number of ionizing radiation hits is not surprising considering the size of the potentially affected populations. Table 1. Internet searches—February 2016. Keyword . + Safety . + PPE, safety . + Clothing, safety . ‘Ionizing radiation’ 730 000 142 000 31 100 RF 717 000 93 500 607 000 EMF 2 570 000 146 000 41 900 Wi-Fi 110 000 000 439 000 3 580 000 Keyword . + Safety . + PPE, safety . + Clothing, safety . ‘Ionizing radiation’ 730 000 142 000 31 100 RF 717 000 93 500 607 000 EMF 2 570 000 146 000 41 900 Wi-Fi 110 000 000 439 000 3 580 000 Table 1. Internet searches—February 2016. Keyword . + Safety . + PPE, safety . + Clothing, safety . ‘Ionizing radiation’ 730 000 142 000 31 100 RF 717 000 93 500 607 000 EMF 2 570 000 146 000 41 900 Wi-Fi 110 000 000 439 000 3 580 000 Keyword . + Safety . + PPE, safety . + Clothing, safety . ‘Ionizing radiation’ 730 000 142 000 31 100 RF 717 000 93 500 607 000 EMF 2 570 000 146 000 41 900 Wi-Fi 110 000 000 439 000 3 580 000 A small random number of ionizing radiation websites offering IR-PPE and similar devices for different anatomical areas were visited. Radio frequency (RF), electro magnetic fields (EMF) and Wi-Fi websites were randomly visited to find RF-PPE stylistically matching the IR-PPE (e.g. hats). RESULTS Literature review The occurrence of two brain tumors in Toronto cardiologists in 1997 and a possible link between occupational fluoroscopic exposure and brain tumors were discussed by Finkelstein in 1998(1). He concluded that the link was biologically plausible but statistically unusual. Hardel reported a case–control study on the risk for brain tumors from ionizing radiation and cellular telephones in 2001(2). Small numbers of cases were identified in both cohorts. Kuon described the benefits of a lead cap in invasive cardiology in 2003(3). His phantom studies documented exposure reduction resulting from the use of this and other radioprotective devices in this environment. Picano reviewed cancer and non-cancer brain and eye effects in 2012(4) and concluded that a systematic assessment is needed. In 2013, Roguin(5) reported on a collection of 31 anecdotal cases of brain cancer in interventional fluoroscopists. He reported that 85% of localized cancers were on the left side. He concluded ‘…provide the basis for speculation regarding chronic radiation exposure and brain tumors…’ Two reports of scatter dose distributions in the fluoroscopic environment(6, 7) demonstrated 2:1 left:right values. Karadag(8) reported dose measurements on the outside a lead cap and lead apron in a clinical environment in 2013. Data were provided with and without the use of the ceiling suspended lead shield. Head measurements were only reported on the wearer's left (both inside and outside the lead cap). Hardell(9) reported the results of a case–control study of malignant brain tumors and mobile-phone use in (cell-phone) 2013. He concluded that ‘These findings provide support for the hypothesis that RF-EFMs play a role in the initiation and promotion stages of carcinogenesis.’ The conclusion of Petterson(10) in 2014 stated that ‘The findings do not support the hypothesis that long-term mobile-phone use increases the risk of acoustic neuroma.’ Hardell(2) provides the only identifiable report discussing brain cancer risk from both occupational fluoroscopy exposure and cell-phone use. This paper does not provide data on the additional risk if cell phones are used by fluoroscopists. Articles such as those outlined above are frequently summarized in newsletters by the medical media. Oftentimes, the carefully stated caveats and limitations in the primary articles are simplified or omitted in the reports for a variety of reasons. Such summaries can be read by non-experts to imply that the observations are established scientific or epidemiological facts. The impression of the certainty of these cancer risks increases when the ‘information’ is further transmitted via internet channels or word of mouth. Advice regarding personal risk reduction in fluoroscopy is frequently published in many venues such as the National Council on Radiation Protection and Measurements, International Commission on Radiological Protection (ICRP), International Atomic Energy Agency, organizational websites, as well as in the scientific literature(11–18). Additional advice on risk reduction is frequently provided on the websites vending IR-PPE and RF-PPE. The quality of this information is quite variable and highly source dependent. Order of magnitude estimate of the cost of averting a fatal ionizing radiogenic brain cancer Economics needs to be considered when setting radiation protection policies. One example is reducing the lifetime risk of a fatal radiogenic brain cancer. At occupational irradiation levels, there is insufficient data in the literature to support a precise analysis of the dose–response function. However, an order of magnitude estimate is possible using the two extreme limits of maximum permitted and zero occupational whole brain irradiation. At the extreme of maximum permitted dose, it is postulated that the whole brain is uniformly irradiated to the current ICRP eye dose limit of 20 mGy y−1 for every year in a 40-y working life. Using ICRP-103, the weighting factor for the brain is 0.01. Thus, the effective dose E associated with a 0.8-Gy irradiation is 8 mSv (for fluoroscopy photons). Applying a nominal 5%/Sv risk of fatal cancer yields an estimated lifetime cancer risk of 4 × 10–4. Risk=20mGyy×40y×0.01(brain weighting factor)×5%/Sv=4×10–4(1) It is noted that observed collar measurements seldom exceed 20 mGy y and are usually much lower. The probability of any individual maintaining 20 mGy y for 40 y is very small. The half-value thickness of fluoroscopic energy photons is a few centimeters. Thus, the peak and average brain dose is a fraction of the collar reading. Thus, the average actual whole brain dose received by a busy operator is likely to be much less than 800 mGy. A perfect protective device is assumed to totally eliminate brain irradiation and its associated risk. Reusable (PD-R) and disposable protective devices (PD-D) are available in the market. The nature and construction of these devices is not relevant to the discussion. PD-R is reusable. Running costs are incurred for: initial purchase, periodic radiation safety checks, maintenance and occasional replacement. PD-D is used for a single procedure and then disposed of. In this analysis, the 40 person-year cost of PD-R is $4000 (40 y × $100/person-year running cost). The cost of PD-D is $40 000 (40 person-year × 100 procedures/person-year × $10/procedure). Secondary benefits of disposable devices (e.g. infection control) are not considered. The order of magnitude cost of averting a fatal brain tumor is the 40-y cost of the device divided by the 40-y avoided risk. Thus Actuarialcost(PD-R)=4×10+3/4×10–4≈$10 00 000 000⁢per averted fatal tumor(2a) Actuarialcost(PD-D)=4×10+4/4×10–4≈$100 000 000per averted fatal tumor(2b) The costs to eliminate one statistical fatal brain cancer are likely to be minimums given the assumptions used in these estimates. As discussed above, the 0.8-Gy lifetime whole brain dose is likely to be unusual. Similarly, few protective devices are capable of totally blocking radiation. Decreased lifetime dose accumulation and/or less than 100% efficient shielding will increase the actuarial cost of averting a fatality. Vendor claims for RF-PPE and related devices Two major classes of ‘protective devices’ were identified on vendor websites. The first class might be called ‘radiation cancelling devices’. Claims for such devices include general discussions of real or presumed RF fields and testimonials from satisfied users. The second class was basically conductive fabrics in a variety of configurations. Claims include measured field strength reduction along with the general discussions and many testimonials. Use of product is generally claimed to reduce a long list of non-specific illness. DISCUSSION General The goals of health physics and safety engineering include both fear and risk reduction. Engineering controls are a preferred method of reducing risk. Unfortunately, a complete engineering control solution is incompatible with either the performance of clinical fluoroscopy procedures or the use of cell phones. PPE or other devices are often used to provide additional protection. Enhancing or introducing new forms of IR-PPE, or other devices, will usually reduce measurable radiation levels. At some point, deploying an additional device is unlikely to yield an economically favorable risk reduction. Some of the questions that should be addressed as part of justifying additional fluoroscopic device deployment include the following: Does the achievable radiation reduction yield an important radiogenic risk reduction? Are the financial costs an appropriate use of limited safety funds? Does device deployment result in important increases of overall patient and/or staff risk? IR-PPE is itself a source of risk because of its weight, its effects on the wearer's ergonomics and as a possible impediment to optimum performance of the clinical procedure. Consider the necessary lead thickness required in a fluoroscopic apron: a 100-mm Pb layer is not ergonomically feasible. A 0.001-mm lead (Pb) layer is light but will not provide substantial protection. Appropriate overall optimization to minimize overall patient and staff risk is seldom performed. Regulations specifying a worst-case minimum Pb thickness (e.g. 0.5 mm) are simple to implement but usually result in radiogenic overprotection without consideration of secondary risks. Vendor claims IR-PPE and related devices IR-PPE is constructed using a variety of materials and may be either disposable or reusable. Although, attenuation characteristics (typically kVp-dependent transmission) of the PPE's materials is occasionally provided, the typical specification is its lead equivalent thickness. The accuracy of even these specifications is degraded when clinical radiation fields do not match those used in the testing laboratory. Of greater importance is the failure to consider the spatial and intensity components of the source term in relation to the clinical use of PPE (e.g. lead gloves). Interactions of PPE with the imaging equipment's automatic dose rate control are seldom discussed by vendors. RF (Wi-Fi) domain Almost all of the material in this domain is directed toward the general public. The common message is that protection is needed from a long list of risks with claimed association to cell phones or Wi-Fi. RF-PPE and similar devices provide electromagnetic shielding. A small fraction of sites provides attenuation data on the bulk material. Very little real-world information on the actual RF fields or attenuation by devices in use is provided. An exception is the market segment providing safety equipment to professional RF workers (such as cell-tower service staff). Risk reduction data are presented on these sites at a level similar to the vendors of IR-PPE. Radiation transformation devices are intended to be placed on cell phones, placed in the environs, or worn in some manner. These devices are widely available in a variety of materials and artistic styles. Their main claim is that their construction transforms dangerous RF fields into a safe variety. Physical measurements demonstrating such transformations could not be found. Their effectiveness is demonstrated by user testimonials. Some ionizing radiation workers similarly believe that their radiation monitors protect them by reflecting or absorbing radiation. Analysis of risks of brain cancer from ionizing and RF irradiation Brain tumors provide a useful focus because of the availability of irradiation information in this anatomical region. Attributing the causation of brain tumors and a long list of other bioeffects(19–21) to occupational fluoroscopic exposure is not statistically supported in the refereed epidemiology literature. Statistical evidence for cell-phone tumor induction is rare, despite an exposed population many orders of magnitude are larger than fluoroscopists. No refereed literature could be identified statistically demonstrating an enhanced cancer risk among these ‘dual users’. However, one cannot totally exclude some possible associations between exposures and brain tumors. Most of the credible papers in both domains end up with a request for further epidemiology. The 2013 Roguin(5) paper reporting cases of brain cancer in interventional fluoroscopists with a left:right ratio of 4:1 has been a focus of attention and concern in the past few years. The original paper suggests fluoroscopic scatter as a cause, indicates that there were too few cases for statistical significance and suggests that other possible cases be identified. As noted above, secondary and tertiary reports about this paper usually ignore the caveats and treat the findings as well-proven epidemiology. Many interventional fluoroscopists accept this ‘fact’ and actively attempt to mitigate their risk by using additional IR-PPE. Operators are exposed to a non-homogeneous scatter field when they work. Fields are generally higher on the operators’ left when they stand on the patient's right side. Scatter field intensities change with beam orientation and the operator's head moves within the field during procedures. Measurements made during clinical series demonstrate left:right gradients below 2:1(6, 7, 22–24). Using the Linear No Threshold Model as a first approximation, this is an indication that the 4:1 cancer rate is either a statistical fluke or is attributable to other factors. Asymmetries in cell-phone ‘induced’ brain cancers have been reported with attempts to correlate these with the side of device use. Confounding factors are the left or right handedness of a user, the use of a cell phone while performing other actions and brain dominance. The overall incidence is more or less the same order of magnitude as fluoroscopically ‘induced’ brain tumors. It is likely that almost all fluoroscopists also use cell phones. However, no literature has been identified discussing cell-phone use as a confounder in fluoroscopic ionizing radiation studies. CONCLUSION A wide range of IR-PPE and an even wider range of RF-PPE are offered on the internet. Products in each domain literally offer head to toe protection. Advertising writers and product endorsers seldom have a scientific or technical background. Their knowledge base can be considered a reflection of the beliefs (both true and false) of the concerned community. Marketing materials in both domains tend to use combinations of: the available scientific literature to support their products where there is any evidence of biological harm; physical attenuation data describing their materials especially in situations where there is little biological evidence; and testimonials reporting perceived health improvements. The absolute health benefits of many of these products typically both vague and overstated. In some cases, misrepresentation can result in decreased safety. However, for most of products, the misrepresentation is likely due to the writers’ willingness to respond to the fears of prospective customers. Individuals and institutions are able to buy a wide variety of safety goods in the open market. However, budgets are finite. A gratuitous purchase of radioprotective equipment reduces the funds available to mitigate other safety risks. Unwarranted user fears derived either from vendor assertions or user hearsay should not be allowed to drive the radiation protection system to the point of decreasing overall safety. REFERENCES 1 Finkelstein , M. M. Is brain cancer an occupational disease of cardiologists . Can. J. Cardiol. 14 ( 11 ), 1385 – 1388 ( 1998 ). Google Scholar PubMed OpenURL Placeholder Text WorldCat 2 Hardell , L. , Mild , K. H., Pahlson , A. and Hallquist , A. Ionizing radiation, cellular telephones and the risk for brain tumours . Eur. J. Cancer Prev. 10 ( 6 ), 523 – 529 ( 2001 ). 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TI - PROMOTING FLUOROSCOPIC PERSONAL RADIATION PROTECTION EQUIPMENT: UNFAMILIARITY, FACTS AND FEARS
JF - Radiation Protection Dosimetry
DO - 10.1093/rpd/ncw307
DA - 2017-04-01
UR - https://www.deepdyve.com/lp/oxford-university-press/promoting-fluoroscopic-personal-radiation-protection-equipment-76MitRilI0
SP - 180
VL - 173
IS - 1-3
DP - DeepDyve
ER -