Ultraviolet A Light Protection in Car Windows
abstract
This abstract is available on the publisher's site.
Access this abstract nowImportance
Ultraviolet A (UV-A) light is associated with the risks of cataract and skin cancer.
Objective
To assess the level of UV-A light protection in the front windshields and side windows of automobiles.
Design
In this cross-sectional study, 29 automobiles from 15 automobile manufacturers were analyzed. The outside ambient UV-A radiation, along with UV-A radiation behind the front windshield and behind the driver's side window of all automobiles, was measured. The years of the automobiles ranged from 1990 to 2014, with an average year of 2010. The automobile dealerships were located in Los Angeles, California.
Main Outcomes and Measures
Amount of UV-A blockage from windshields and side windows. The average percentage of front-windshield UV-A blockage was 96% (range, 95%-98% [95% CI, 95.7%-96.3%]) and was higher than the average percentage of side-window blockage, which was 71% (range, 44%-96% [95% CI, 66.4%-75.6%]). The difference between these average percentages is 25% (95% CI, 21%-30% [P < .001]). A high level of side-window UV-A blockage (>90%) was found in 4 of 29 automobiles (13.8%).
Conclusions and Relevance
The level of front-windshield UV-A protection was consistently high among automobiles. The level of side-window UV-A protection was lower and highly variable. These results may in part explain the reported increased rates of cataract in left eyes and left-sided facial skin cancer. Automakers may wish to consider increasing the degree of UV-A protection in the side windows of automobiles.
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Additional Info
Disclosure statements are available on the authors' profiles:
Assessment of Levels of Ultraviolet A Light Protection in Automobile Windshields and Side Windows
JAMA Ophthalmol 2016 May 12;[EPub Ahead of Print], BS Boxer WachlerFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
Now the lentigo simplex on the left side of my face makes more sense! This review from the ophthalmology literature has implications for dermatology, especially for those (like me) who do not use sunscreen daily unless they're planning to be outside. I know many of my colleagues are shocked when I tell them I'm not a religious daily sunscreen user, but I'm a relatively low-maintenance person when it comes to "grooming," and that one extra step often evades my routine. This potential flaw in health habit lets me be more empathetic to patients who need daily sunscreen more than I do (I'm a type III skin), although I think I'll go apply sunscreen before I head to work this morning as that lentigo really annoys my wife (probably more than me!).
A few tips from this article:
In a study done by Dr. Brian Boxer Wachler, he assesses the level of UV-A light protection in the front windshields and side windows of 29 automobiles, ranging from 15 automobile manufacturers in the Los Angeles area. The automobiles ranged from the year 1990 to 2014, with the average year of 2010. The results indicated that the UV-A protection for the front windshield was 96%, making it higher than the average percentage of side-window blockage which was at 71%. The present study can explain the increased rates of cataract in the left eye as well as left-sided facial skin cancer. The proposed solution would be to install a clear non-tinted UV film to protect the side windows.
We have long known that glass does a good job of blocking UVB but not UVA light. This study in the ophthalmology literature presents some fascinating data on the amount of UVA light that passes through windshields vs side windows in a selected group of automobiles from different makers and different years. The variability in UVA blocking in the side windows was remarkable.
I spend the majority of my clinical time taking care of two groups of people: patients suffering from facial skin cancers (Mohs and cutaneous oncology practice) and patients wishing to reverse the effects of chronological and photo-aging (laser and cosmetic practice). A big portion of the counseling in both clinics is on prevention of the effects of UV light on the skin through sun protection and avoidance.
Here is the discussion that I have with almost every patient (easier for me to do in my clinics rather than in medical dermatology clinics because people undergoing surgery for skin cancers or electively spending on cosmetic treatments are already motivated more than the average patient for obvious reasons).
Currently, I discuss the importance of the daily (meaning EVERY day of the year) use of a broad-spectrum (meaning UVA and UVB) blocking sunscreen with an SPF of 30 or greater on the face, neck and ears, as well as other exposed areas. In addition, I recommend reapplication of the sunscreen if they will be exposed to sun (traveling in a car, being near windows indoors, or being outdoors). Many men and women are able to pull off the reapplication by the use of a physical blocking (titanium dioxide– and zinc oxide–based) powdered sunscreen, which they can brush on easily without getting their hands greasy. This increases the chances that men will do it (since it is easy and it does not require washing hands afterwards) and the chance that women will do it (because they can apply it right over their makeup).
Also, since we do discuss sun avoidance and sun protective clothing, hats, and sunglasses, I take the extra step to discuss vitamin D. I simply have them ask their primary care doctor to check their vitamin D level at their next visit. I also inform them that in case it is low, it is easily replaced with over-the-counter or prescription supplements. The primary care doctors are experts on this and can recommend replacement based on the most current guidelines.
An observation I have made in practice is that there are a large number of skin cancer patients who are grade school teachers, gardeners, golfers, outdoor athletes, sales people, truck drivers, and pilots. The association is hard to ignore. For all of these people, the recommendations above are helpful. For the drivers and sales people, I can now recommend UVA protective film on the car windows.
Furthermore, being a pilot and an aviation enthusiast, I remind my patients that are helicopter and airplane pilots (both recreational and commercial) that for every 1000 feet of altitude we are exposed to approximately 4% more UV radiation. There have been recent studies pointing out that commercial pilots have a higher incidence of skin cancers; however, now they may consider looking at the UV protection in their aircraft. At the very least, I preach the same sun protective behavior as above. Many people have seen me put on the powdered sunscreen at the airport and golf course and have adopted it too.
In the end, we can’t make anyone do anything, but educating them on how to best protect themselves with daily habits during their visit and also by example is a duty we should take seriously.