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wileyonlinelibrary.com/journal/phpp Photodermatol Photoimmunol Photomed. 2018;34:330–337.
© 2018 John Wiley & Sons A /S.
Publish ed by John W iley & Sons Ltd
1 | INTRODUCTION
Skin cancer is the most common cancer in light- skinned popula-
tions worldwide and is mainly caused by excessive exposure to
solar ultraviolet radiation (UVR).1-3 Nonmelanoma skin cancer is
predominantly associated with total cumulative UVR exposure,
leaving the most exposed skin zones, such as the face, back of
the neck, eyes and ears, at high risk.4 -7 Solar UVR doses received
by an individual are highly influenced by skin phototype, time and
duration of exposure, environmental factors, and sun- protective
behaviour and attitudes.2 Indeed, increasing skin cancer rates are
mainly attributed to changing lifestyles over the last decades from
sun avoidance towards sun- seeking behaviour with positive per-
ception of sunbathing, fashion trends favouring lesser body cloth-
ing coverage, more outdoor activities and more holidays spent in
sunny destinations.8,9
Accepted: 17 April 2018
DOI : 10.1111 /phpp.1238 8
ORIGINAL ARTICLE
Facial exposure to ultraviolet radiation: Predicted sun
protection effectiveness of various hat styles
Claudine Backes1,2 | Arianna Religi3 | Laurent Moccozet3 | Laurent Vuilleumier4 |
David Vernez1 | Jean-Luc Bulliard2
1Institute for Work and Healt h, University
of Lausanne and Geneva, Lausanne,
Switzerland
2Centre Hospitalier Universitaire
Vaudois, U niversi ty Institute of Social and
Preventive Medicine (IUMSP), University of
Lausanne, Lausanne, Switzerland
3Computer Science Centre, Information
Science Institute, University of Geneva,
Geneva, Switzerland
4Federal Office of Meteor ology a nd
Climatology (Me teoSwiss), P ayerne,
Switzerland
Correspondence
Claudine Backes, Centre Hospitalier
Universitaire Vaudois (CHUV), University
Instit ute of Social and Preve ntive Medicine
(IUMSP), University of Lausanne, Lausanne,
Switzerland.
Email: claudine.backes@chuv.ch
Funding Information
This work w as suppo rted by the Swiss
Nationa l Science Foundation (SNF, grant no.
CR23I3 152803).
Summary
Background/Purpose: Solar ultraviolet radiation (UVR) doses received by individuals
are highly influenced by behavioural and environmental factors. This study aimed at
quantifying hats’ sun protection effectiveness in various exposure conditions, by
predicting UVR exposure doses and their anatomical distributions.
Methods: A well- defined 3- dimensional head morphology and 4 hat styles (a cap, a
helmet, a middle- and a wide- brimmed hat) were added to a previously published
model. Midday (12:00- 14:00) and daily (08:00- 17:00) seasonal UVR doses were esti-
mated at various facial skin zones, with and without hat wear, accounting for each
UVR component. Protection effectiveness was calculated by the relative reduction in
predicted UVR dose, expressed as a predictive protection factor (PPF).
Results: The unprotected entire face received 2.5 times higher UVR doses during a
summer midday compared to a winter midday (3.3 vs 1.3 standard erythema dose
[SED]) with highest doses received at the nose (6.1 SED). During a cloudless summer
day, the lowest mean UVR dose is received by the entire face protected by a wide-
brimmed hat (1.7 SED). No hat reached 100% protection at any facial skin zone
(PPFmax: 76%). Hats’ sun protection effectiveness varied highly with environmental
conditions and was mainly limited by the high contribution of diffuse UVR, irrespec-
tive of hat style. Larger brim sizes afforded greater facial protection than smaller brim
sizes except around midday when the sun position is high.
Conclusion: Consideration of diffuse and reflected UVR in sun educational messages
could improve sun protection effectiveness.
KEYWORDS
prevention, protection effectiveness, skin cancer, sun exposure, ultraviolet radiation (uv)
|
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BACKES E t Al.
Prevention campaigns have long raised awareness about sun
exposure hazards and recommended skin and ocular protection
measures such as seeking shade, avoiding peak irradiances (11:00-
15:00), using sunscreen and wearing a hat, sunglasses and long
sleeves.10-13 Sun protec tion effectiveness is generally conveyed by
means of indexes of protection such as the sun protection factor
(SPF) for topical sunscreen or the ultraviolet protection factor (UPF )
for garment. The dose reduction expressed by such factors does not
clearly inform the public about how much solar UVR is transmitted
to the skin when using such sun protec tion means.14
The few previously published studies estimating the UVR doses
received by the head used individual dosimetric measurements on
manikin head forms, and reported high exposure for several facial
zones, with or without hat protec tion.15,16 Dosimetric measure-
ments are costly, time- consuming, contex t- specific, prone to be-
havioural bias, and, importantly, cannot distinguish direct, diffuse
and reflected UVR components reaching the skin. Diffuse UVR has
recently been shown to contribute substantially to the total UVR
dose received, a fact probably underestimated in current prevention
messages.17
To address these issues, a previously developed 3- dimensional
(3D) numeric modelling tool predicting solar UVR doses at differ-
ent anatomical sites, taking into account each UVR component
(direct, diffuse and reflected UVR), has been enhanced.5 With the
aim to quantify sun protection effectiveness, a specific morphol-
ogy with precisely defined facial zones has been created for the
head and various 3D hat styles have been added to the model.18 ,19
To assess UVR doses received by the face and support effec tive
prevention messages, adapted to various environmental situa-
tions, this study aims (i) to predict midday (12:00- 14:00) seasonal
sun protection effectiveness and UVR dose reduction in various
hat styles for different facial zones and (ii) to estimate the daily
(08:0 0- 17:00) dose reduction in direct, diffuse and reflected UVR
received at various facial zones when wearing a commonly used
hat style (a baseball cap).
2 | MATERIAL AND METHODS
2.1 | Modelling tool
Solar UVR doses potentially received by facial skin zones were es-
timated by SimUVEx v.2 (Simulating UV Exposure version 2.0). This
model uses irradiance data and 3D human body modelling, as well
as computer graphics techniques, to estimate skin exposure doses
within minutes.
The principles of this model and its on- field validation with do-
simetry measurements were detailed previously.5,17,18
This study focuses on the facial skin zones of a detailed adult
head morphology. The numeric model delineates 33 skin zones for
the head, highlighted in various colours (Supporting Information
Figure S1a,), and which complies with the topography of the
International Classification of Diseases for Oncology.20 The tool in-
cludes static and dynamic functionalities, as well as a rotation step,
which can be selected according to each exposure situation chosen.
2.2 | Input data
2.2.1 | Ambient irradiance data
Direct, diffuse and reflected er ythemally weighted UV irradi-
ance, measured every minute at the MeteoSwiss Payerne Station
(46.815°N, 6.944°E, altitude 491 m) for the year 2014, was used
for this study. The Payerne station is part of the Baseline Surface
Radiation Network of the World Meteorological Organization,
World Climate Research Program, and uses broadband UV radiom-
eters with filters mimicking the erythema response.21
Ambient irradiance data used hereafter refers to midday sun
exposure (12:00- 14:00) and daily sun exposure (08:00- 17:00).
Potentially received facial UVR doses were estimated for 1 day per
season (Table 1), taking into account cloudless exposure conditions
and albedo (reflection coefficient s for reflecting ground surfaces).22
By selecting days of a t ypical cloudless situation, worst- case scenar-
ios regarding seasonal UVR were chosen. For midday simulations,
a static orientation was assumed (ie reading a book, sunbathing or
working outdoors in a predominantly static position) and the fixed
head orientation option was chosen. For daily simulation runs
(08:0 0- 17:00), a dynamic orientation was presumed and a 24° step
rotation per minute was selected.
2.2.2 | Hats and facial skin zones
Four hat styles, based on real- life observations, were implemented
in the model (Figure 1): (1) a baseball cap (10 cm frontal brim
size), often used in leisure and working environments, (2) a small-
brimmed hat same sized as a helmet, used for instance in con-
struction work (7 cm frontal brim size, 4 cm lateral brim size), (3)
Season Simulated day
Exposure duration
(for all hat s)
Exposure duration
(cap- case)
Weather and
setting
Spring 09 April 12:00- 14:00 08:00- 17:00 Cloudless
Summer 17 July 12:00- 14:00 08:00- 17:00 Cloudless
Autumn 30 October 12:00- 14:00 08:00- 17:00 Cloudless
Winter 31 December 12:00- 14:00 08:00- 17:00 Cloudless
and high
albedo
TABLE1 Simulation exposure
conditions for each selected seasonal day
of the year 2014
332
|
BACKES Et Al.
a middle- brimmed hat (6 cm circular brim size), which corresponds
to the minimal brim size recommended for sun protection, and (4)
a wide- brimmed hat (17 cm circular brim size).23 -26 The 17 cm brim
size represents a theoretically ideal brim size for high sun protec-
tion on a summer day, obtained after varying the virtual brim size
of the hat morphology. The fabric of all hats was considered to
provide full protection for all covered facial skin zones (blocking
100% UVR).
The skin zones of the entire face included (i) the ears (mean
dose received by auricular, earlobe, and earlobule front/back at
the right and left ear); (ii) the ocular region (mean dose received
by tear duct, upper, lower and lateral ocular region at left and
right ocular region); (iii) the nose (dose received by columnella,
external nose, tip of the nose and dorsum nasal); (iv) the cheeks;
(v) the jaws; (vi) the chin; and (vii) the lower lip. Midday (12:00-
14:00) UVR doses received by the above- enumerated skin zones,
the entire face and the neck were estimated separately. The daily
(08:0 0- 17:00) UVR dose reduction provided by a commonly used
headgear such as a baseball cap with no flag was estimated sepa-
rately for (i) the left ear, (ii) the nose, (iii) the oral region (including
upper and lower lips) and (iv) the forehead (subzone of the top of
the head: Supporting Information Figure S1a).
2.3 | Output data
2.3.1 | Solar UVR doses and predicted protection
factor (PPF)
The estimated solar UVR doses received are reported in standard ery-
thema dose (SED).27 The UVR doses reported represent doses poten-
tially received, calculated by summing up the estimated direct, diffuse
and reflected UVR for each day and skin zone. The sun protection ef-
fectiveness of each hat style was determined by comparing the solar
UVR dose potentially received with and without a hat for each facial
skin zone for the same exposure duration. The sun protection effec-
tiveness is expressed as a PPF (%), representing the relative reduction
in predicted UVR dose for any facial zone (Equation 1). The greater the
PPF, the higher the relative sun dose reduction is
Equation 1: Predictive protection factor (PPF [%]) calculation, esti-
mated for UVR dose received at each facial zone with and without
protection.
3 | RESULTS
Total solar UVR doses potentially received by the entire face, and by
each facial skin zone, with and without hat protection, during midday
exposure (12:00- 14:00), are given in Table 2 for one day per season.
Overall, large variations in UVR doses across facial skin zones are
observed within a season and, to a lesser extent, between seasons.
During a 2- hour midday exposure, the unprotected face poten-
tially receives 2.5 times more UVR doses in summer than in winter
(3.3 SED vs 1.3 SED). Without hat protection, the nose received the
highest dose estimated and the largest seasonal dose variation (sum-
mer/winter ratio of 4.4) compared to other facial skin zones, while
the chin had the least seasonal dose variation (summer/autumn ratio
of 1.9). Midday summer exposure ranged by a factor of 4.5 across
unprotected facial skin zones, from 1.4 SED at the chin to 6.1 SED
at the nose. In winter, UVR doses without a hat protection varied by
a factor of 0.4 (from 1.1 SED at the ears vs to 1.5 SED at the lower
lip and cheeks), with values in- between summer and winter ones ob-
served for spring and autumn.
With headgear prote ction, on a cloudless summer day, the lowest
mean UVR dose received by the entire face was found with a wide-
brimmed hat (1.7 SED). The UVR doses potentially received by the
entire face were comparable for all other hat styles (2.0 SED). While
little difference was observed in sun protection afforded by hat
styles for the entire face in winter, a baseball cap yielded the same
lowest mean UVR dose as a wide- brimmed hat in autumn. The mid-
dle size brimmed hat in springtime and the helmet or small- brimmed
hat in autumn exposed the entire face to the largest potential UVR
doses. In summer, doses received at the neck were reduced by the
circular brim of some hats (small- , middle- and wide- brimmed hats).
However, in winter, these hats provided almost no dose reduction.
The PPF of each hat style is reported for each seasonal day in
Figure 2 (Figure 2: summer and winter; Supporting Information
Figure S2a: spring and autumn). PPF values showed high intersea-
sonal variability for most facial skin zones for direct UVR only in
cloudless situations. No hat could provide a 100% sun protection
for any facial skin zone during any season (maximal protection: 76%
for the nose in summer with a baseball cap). Overall, the PPF val-
ues of hats were greater in summer and spring than in winter and
autumn. The effectiveness was lowest in winter for each hat and
ranged from 0% to 37% across facial skin zones. Wearing a base-
ball cap on a cloudless day result s in PPF values of 60% and 10%
at all seasons for diffuse and reflected UVR, respectively, whereas
the degree of protection from direct UVR was season- dependent
PPF[%]
=
UV
withoutprotection −
UV
withprotection
UV
withoutproduction
×
100
FIGURE1 Head with dif ferent hat
styles (brim size [cm]): 1. baseball cap
(10 cm frontal); 2. helmet or small-
brimmed hat (7 cm frontal, 4 cm lateral); 3.
middle- brimmed hat (6 cm, circular); or 4.
wide- brimmed hat (17 cm, circular)
1. Baseball
cap
2. Helmet or small-
brimmed hat
3. Middle-brimmed
hat
4. Wide-brimmed
hat
|
333
BACKES E t Al.
(PPF: 79% in summer, 60% in spring, 41% in autumn and 29% in win-
ter, Supporting Information Figure S2c).
The chin was the facial zone, the least protec ted by any hat style,
with the lowest PPF for all seasons. The nose showed the highest
PPF of all facial zones in summer and was the skin zone for which
the relative UVR dose reduction was the least dependent on the hat
style worn. Wearing a baseball cap offered the least protec tion of all
hats for the ears, with a UVR dose reduction of 20- 25% (compared
to 50% for a helmet), but the highest protection for ocular and nasal
regions during all seasons. For all hat styles, the lower lip and the
ocular region appeared to be the zones for which sun protec tion ef-
fectiveness was the most season- dependent.
The daily (08:00- 17:00) seasonal cumulative dose of each solar
UVR component was estimated for 4 skin zones covered by a base-
ball cap (Figure 3 (i) a summer day and (ii) winter day; Supporting
Information Figure S3a: (i) spring and (ii) autumn, Suppor ting
Information). In the absence of hat protection, the direct and dif-
fuse UVR during cloudless situations follow a bell- shaped pattern.
On a cloudless winter day with snow covered ground (high albedo),
the contribution of UVR reflec ted from the ground increased mate-
rially. Overall, diffuse radiation is the main contributor to the tot al
daily solar UVR dose received, while direct radiation predominates in
summertime only. Results were comparable for other implemented
hat styles (data not shown).
In summer, the direct UVR potentially reaching the nose and
the oral region is totally blocked by a baseball cap around midday,
whereas the diffuse radiation is only reduced by half. In comparison
with other facial zones, the dose reduction in direct and dif fuse UVR
at the ears is small. The dose reduction is largely dependent on the
sun position (daytime and exposure situation). The nose for example
is protected during long daily period when the sun position is high;
however, this period is impor tantly reduced when the sun is low.
Albeit the total UVR is low in winter, the reflected UVR dose is
almost as high as the direct UVR with snow on the ground. The re-
duction in the reflected UVR dose received by each skin zone is ver y
small when wearing a baseball cap, but direct and diffuse UVR doses
are almost totally reduced at the forehead. In situation when the sun
position is low, especially in winter, the shade provided by the hat
does not necessarily cover all facial zones (Figure 3).
The influence of the sun position towards the total solar UVR re-
ceived is illustrated for a day in summer and in winter (Suppor ting
Information Figure S 4). The sun position is given by the solar zenith
angle (SZA), which is the angle between the zenith and the centre of
the sun’s disc (position of the sun = 90°- SZA). At midday, the solar
FIGURE2 Predictive protection factors
(PPF [%]) by hat style and facial skin zone in
(i) summer and (ii) winter for 2-hours midday
exposure [Colour figure can be viewed at
wileyonlinelibrary.com]
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Ear Eye Nose Cheek ChinJaw Lower Lip Neck
PPF
(i) Summer
Cap Middle-brimmed hat Wide-brimmed hat Helmet
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Ear Eye Nose Cheek Chin JawLower Lip Neck
PPF
(ii) Winter
Cap Middle-brimmed hat Wide-brimmed hat Helmet
334
|
BACKES Et Al.
FIGURE3 Direct, diffuse and reflec ted ultraviolet radiation (UVR) dose estimates for facial skin zones with and without protection from
a baseball cap on a day in (i) summer and in (ii) winter. Solid line represents the dose received without head protection in a particular skin
zone for all 3 radiation component s. Dashed lines are used to represent UVR dose potentially received in the case of head protection
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00
Dose (J/m2)
Hour
Ear
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00
Dose (J/m2)
Hour
Nose
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00
Dose (J/m2)
Hour
Forehead
Diffuse with protecon Direct with protecon
Diffuse without protecon Direct without protecon
14:00 16:00 18:00 20:00 22:00
Reflected with protecon
Reflected without protecon
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
0:00 2:00 4:00 6:00 8:00 10:0012:0014:00 16:00 18:00 20:00 22:00
Dose (J/m2)
Hour
Oral region
Diffuse with protecon Direct with protecon Reflected with protecon
Diffuse without protecon Direct without protecon Reflected without protecon
(I) Summer
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00
Dose (J/m2)
Hour
Ear
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00
Dose (J/m2)
Hour
Nose
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
0:00 2:00 4:00 6:00 8:00 10:0012:00 14:0016:00 18:0020:00 22:00
Dose (J/m2)
Hour
Forehead
Diffuse with protecon Direct with protecon Reflected with protecon
Diffuse without protecon Direct without protecon Reflected without protecon
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00
Dose (J/m2)
Hour
Oral region
Diffuse with protecon Direct with protecon Reflected with protecon
Diffuse without protecon Direct without protecon Reflected without protecon
(II) Winter
|
335
BACKES E t Al.
zenith angle is lowest and consequently the UVR dose received was
highest for each unprotected facial zone. While the solar UVR dose
reduction for each zone is important in summer (with a maximal value
at noon), the dose reduction in winter is comparatively very small.
4 | DISCUSSION
Predic ting the facial su n protection ef fectiveness of v arious hat sty les
has enabled to quantify the UVR dose reduction and to improve our
understanding of the most /least facial skin zones protected under
different environmental conditions, accounting for the effect of di-
rect, diffuse and reflected UVR component s. To our knowledge, this
is the first study to comprehensively address and assess the protec-
tive and environmental contributors of facial UVR exposure. The
estimated UVR doses received at different facial zones vary highly
and differ strongly with environment al conditions. Although hat
protection attenuated the variability in UVR exposure across facial
skin zones, our results show that no hat fits all situations and un-
derline the impor tance of adapting sun protection use to surround-
ing conditions. For most facial skin zones, a wide- brimmed hat is the
most effective hat style, in particular during peak summer irradiance.
However, its effectiveness depends on the considered skin zone and
the sun position. It should be reminded that the relative dose reduc-
tion expressed by the PPF does not indicate the amount of UVR
reaching the skin or the risk associated with the dose received.
Our dose estimates are in line with previous estimates of pro-
tection provided by various hat s and confirmed overall the greater
facial sun protection effectiveness of larger brim sizes as they pro-
vide proportionally more facial shading in par ticular when the sun is
high (and the SZA is low).15,16 ,28-3 0 During clear- sky conditions, hats
with a large frontal brim provide high sun protection for the nose,
but negligible protection for the ears, assuming no hair protec tion in
the simulation model. This explains why a baseball cap with a 10 cm
frontal brim pull low down to the face is, compared to the other im-
plemented hats, the most sun protective for nasal and ocular regions
and as effective for nasal and ocular zones as a wide- brimmed hat
in autumn, when the sun position is lower. From an occupational
perspective (apart for safety), our implemented helmet protected
all skin zones better from the sun than a baseball cap thanks to its
additional circular brim.
Although the ambient UV irradiance in winter in many coun-
tries does not require hat wear for sun protection, it is useful to
better quantify and understand the contribution of reflected UVR
and link this understanding to other reflecting conditions. Our find-
ings show that reflected UVR dose reduction afforded by any hat is
TABLE2 Estimated ultraviolet radiation (UVR) dose (SED)a at various facial skin zones for 4 hat styles, on a cloudless day per season of
the year 2014 [Colour Table can be viewed at wileyonlinelibrary.com]
Hat style
Midday exposure
(12:00- 14:00)
Solar UVR dose (SED)
Entire facebEars Ocular region Nose Cheeks Chin Jaws Lower Lip Neck
Spring 2.7 2.5 2.9 4.7 4.2 1.3 1.9 4.7 1.6
Summer 3.3 3.2 2.5 6.1 4 .9 1.4 2.5 4.4 2.1
Autumn 2.4 1.1 1.5 2.0 1.9 0 .7 1.0 2.1 2.1
Winter 1.3 1.1 1.3 1.4 1.5 1.2 1.2 1.5 1.2
Spring 1.7 1.9 0.7 1.3 1.9 1.2 1.7 3.8 1.5
Summer 2.0 2.5 0.9 1.6 2.2 1.2 2 .1 2.5 2.0
Autumn 1.0 0.9 0.4 1.3 1.4 0.7 0.9 1.8 0.8
Winter 1.1 0.9 0.9 1.0 1.2 1.2 1.2 1.3 1.2
Spring 1.9 0.9 1.2 3.0 3.0 1.2 1.8 4.0 1.4
Summer 2.0 1.3 1.6 2.3 2.7 1.3 2.1 3.3 1.7
Autumn 1.1 0.7 1.3 1.7 1.7 0.7 1.0 1.9 0.7
Winter 1.2 0.7 1.2 1.2 1.3 1.2 1.2 1.4 1.1
Spring 1.3 0.9 0.9 1.2 1.6 1 .1 1.5 2.3 1.3
Summer 1.7 1.3 1.3 1.8 2.1 1.1 1.8 2.3 1.5
Autumn 1.0 0.6 0.7 1.4 1.5 0.7 0.9 1.8 0.7
Winter 1.1 0.8 1.1 1.0 1.2 1.2 1.2 1.3 1.1
Spring 1.7 1.2 0.8 1.8 2.3 1.2 1.7 3 .9 1.4
Summer 2.0 1.6 1.1 2.0 2.5 1.2 2 .1 2.8 1.8
Autumn 1.3 0.6 0.7 1.4 1.6 0.7 0.9 1.9 0.7
Winter 1.1 0.7 1 .1 1.1 1.3 1.2 1.2 1.3 1.1
aCIE standard er ythema dose (SED) (1SED = 100 J/m2 CIE weighted).
bIncluding the ears.
336
|
BACKES Et Al.
low. Hats’ effectiveness depends on the sun position, which is low
around midday in winter so the direction of the solar UVR reaching
the face is frontal. Thus, sun radiation hits the face even if a hat is
worn. When the sun is low (and the SZA is high), the sun protection
capability of small- or middle- brimmed sizes hats is reduced due to
the UVR dose distribution to more vertical facial skin zones.4 Wide-
brimmed hats are most effective when the sun is low (as in spring,
winter, autumn, or summer mornings and evening) and provide no
further protection at summer midday than smaller brimmed hats.
The sun protection effectiveness provided by any hat was very
low at facial zones where skin cancer and prec ancerous skin lesions
commonly occur.31-33 The chin was the least protected facial zone
by any hat style for all seasons. Best sun protected zones were the
eyes, the ears, the nose and the cheeks; however, their protection
effectiveness was highly reduced when reflected UVR was existing.
Throughout the year, during cloudless conditions, the sun protection
effectiveness of hats is mainly influenced by facial exposure to direct
UVR (similar PPF values for diffuse and reflected UVR, Supporting
Information Figure S2b). Our findings underline the importance of
integrating diffuse and reflected radiation into sun dose estimates
and prevention messages. The association between daily UVR doses
received by facial zones and sites of lesion occurrence is moderate
and needs further investigations.
This study has several limits. First, the predicted absolute UVR
doses might be overestimated as no additional sun protection means
(as shade, make- up, sunscreen or sunglasses) or facial (as a beard) or
scalp/ears hair protection were included into the simulations, and a
well- positioned hat wear was assumed during the entire exposure
conditions (no wind) with no clouds in the sky. Thus, the UVR dose
reduction, as expressed in relative terms by the PPF, should be lit-
tle affected by these study assumptions. Second, the scenario with
a circular brim size hat of 17 cm is almost not usable in everyday life,
especially in occupational settings. Its virtual implementation was only
intended to represent the ideal sun protection during summer when
no additional sun protection was used. This very large virtual brim-
sized hat, unlikely to be worn by most of the general public, highlights
the need an adapted combination of different sun protection means
to keep the brim- sized usable. Third, the hat fitting on the forehead
influences the sun protection at various skin zones. Although we did
not assess hat geometry specifically, the 3D fitting of the middle- sized
hat on our head form was slightly deeper suited in the forehead than
the wide- brimmed hat. Consequently, a marginally higher UVR dose
for the ears with a wide- brimmed than a middle- brimmed hat was es-
timated for summer and winter (Table 2).
Skin cancer prevention messages lack quantitative and contex t-
specific data on the effectiveness of sun protection means taking
into account factors affecting the UVR exposure as ground reflec-
tion and sun position, hat style and cumulative exposure doses. Our
study’s findings can help to close a knowledge gap in sun protection
understanding and may lead to revisit some educational messages.
Sun protec tion messages need to clearly emphasize that no hat fits
all situations and their use should be combined with avoidance of
peak radiations periods, shading structures, a neck flag, a scarf,
sunglasses and/or sunscreen in high UV irradiance situations, such
as being in the snow, on light ground surface or in the sand. A use
of UVR exposure models to measure and illustrate sun protection
effectiveness of other specific sun protection means, such as sun-
glasses or shading structures, is warranted.
CONFLICT OF INTEREST
The authors declare no conflict of interest.
ORCID
Claudine Backes https://orcid.org/0000-0003-3300-4959
Jean-Luc Bulliard https://orcid.org/0000-0001-9750-2709
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SUPPORTING INFORMATION
Additional suppor ting information may be found online in the
Suppor ting Information section at the end of the article.
How to cite this article: Backes C, Religi A, Moccozet L,
Vuilleumier L, Vernez D, Bulliard J-L . Facial exposure to
ultraviolet radiation: Predicted sun protection effectiveness
of various hat styles. Photodermatol Photoimmunol Photomed.
2018;34:33 0–337. htt ps://doi.org/10 .1111/phpp.12388
Supporting information:
Figure 1a: Skin zones of the entire head (total skin area: 3864 cm2) are highlighted by specific colours
according to the ICDO-3 coding system. Following skin zones are defined: top of the head: forehead, top;
back head; face: cheeks , jaws, chin; temple; ocular region: tear-duct, upper, lower, lateral; ears:
auricula, earlobe, earlobule front, earlobule back; nose: columella, external nose right, external nose
left, tip of the nose, dorsum nasale; oral region: upper lip, lower lip, orbicularis oris and neck: front,
back.
Figure 1b: Rendering example of head morphology without and with a hat type for fixed simulations for
a spring day (09.04.2014) and cumulative dose of a one-hour exposure (11:00-12:00). (1. head without a
hat, 2. head with a baseball cap, 3. head with brimmed hat, 4. head with helmet, 5. head with wide-
brimmed hat).
Figure 2a: Predictive Protection Factors (PPF [%]) by hat style and facial skin zone in (i) spring and (ii)
autumn.
Figure 2b:
Seasonal Predictive Protection Factor (PPF [%]) of each UVR component (direct, diffuse and reflected) for the facial
skin zones of the ocular region, protected at midday (12:00 – 14:00) by a baseball cap.
Figure 3a: Direct, diffuse and reflected UVR dose estimates for facial skin zones with and without protection from a baseball cap over a cloudless day i. in
spring and ii. in autumn. Solid line represents the dose received without head protection in a particular skin zone for all three radiation - components.
Dashed lines are used to represent UVR dose potentially received in the case of head protection with a baseball cap.
i. Spring
ii. Autumn
Figure 4: Solar Zenithal Angle (SZA) and solar UVR dose variation for four skin zones (forehead, oral region, nose
and ear) unprotected and protected by a baseball-style cap for a day in i. summer and in ii. winter
ii. Winter
i. Summer
