Farm workers’ exposure to high percentage of ambient UVR in Limpopo – a pilot study Ms Karlien Linde*●, Ms Mahlako Nkogatse* and Dr Caradee Wright#.
• Department of Physiology and Environmental Health, University of Limpopo # CSIR Climate Studies, Modelling and Environmental Health Research Group ● presenting author: email:
[email protected]
INTRODUCTION
Ultraviolet radiation (UVR) forms part of the electromagnetic spectrum of sunlight (CIE, 1999). Only UVA (315 nm - 400 nm) and UVB (280 nm – 315 nm) reaches the earth surface (CIE, 1999; IARC, 1997) The ozone layer absorbs UVC spectrum (IARC, 1997).
Figure 1: UVR in the electromagnetic spectrum
INTRODUCTION (cont.)
Exposure to UVR has both positive and negative health effects: Positive effects - the synthesis of Vitamin D (Norval et al., 2007)
Negative health effects -
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Human carcinogen : melanoma and non-melanoma skin cancers such as basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), immune suppression and cataracts; (IARC, 2014; Ahmed et al., 2008; Norval et al., 2007)
Figure 2: An example of a malignant melanoma
Figure 3: Example of a squamous cell carcinoma (left) and a basal cell carcinoma (right)
Acute severe sunlight exposure closely associated with the development of melanoma and BCC (Gandini et al., 2005; Downs et al., 2014;). However, uninterrupted exposure such as working in an outdoor environment for their whole shift still risk factor for skin cancer although to a lesser degree (Gandini et al., 2005; Downs et al., 2014; Wolska, 2013).
Factors that influence individual’s exposure to solar UVR include:
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season, latitude, altitude, type of environment; and the ambient weather plays an important part in the (Hammond et al., 2009; Moehrle et al., 2003a).
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additional factors that determine sunburn risk include:
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skin type, individual’s activity; and work posture (Antoine et al., 2007; Wright et al., 2011).
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Table 1:Fitzpatrick skin phototype classifications with personal solar UVR exposure required for sunburn Skin type and unexposed skin colour
UVR sensitivity to sunburn
Constitutive characteristics
History of sunburn
I - white,
extremely sensitive
Fair skin, blue or light eyes and freckles
Always burns on minimal exposure
II - white
very sensitive
Red or blonde hair, blue, hazel or brown yes and freckles
Burns very readily, freckles common
III – white or light brown
moderately sensitive
Brown hair and blue, hazel or brown eyes
May burn on regular exposure with o protections, tans slowly
3-5
IV- light brown
relatively tolerant
Brown hair and dark eyes
Burns rarely, tans rapidly with minimal exposure
4.5-6
V – brown
variable
Brown yes and dark brown or black hair
Despite pigment may burn easily on exposure
6-10
VI- black,
relatively insensitive
Brown eyes and dark brown or black hair
Rarely burns, though sunburn is difficult to detect on heavily pigmented skin
10-20
( adapted from Wright et al., 2013; CEN 14255-3, 2008)
Continuous UVR exposure estimated to elicit sunburn on untanned skin (SED)
2-3 2.5-3
AIM
To evaluate the personal UVR exposure of individuals regularly working outside on a farm in the Limpopo province during winter.
METHODOLOGY Location and subjects Location : a farm located in the Limpopo province, (latitude 23˚S, longitude 29˚E). Subjects: six farmworkers working in the outside environment of the farm. Work activities included working with livestock such cattle, goats and pigs, as well as crop production. Instrumentation Personal UVB exposure – data-logging UVR badge. UVR badge: photodiode – records UVR level every few seconds.
METHODOLOGY (cont.) Sampling and calibration UVR badges were placed on subjects’ wrists. Ambient UVR: UVR badge was placed on a horizontal plane in direct sunlight. Calibration: research-grade solar UVB biometer (South African Weather Service in Pretoria) before and after sampling. Downloaded UVR in standard erythemal dose (SED). SED = erythemal effective radiant exposure to UVR (Diffey, 2002). The results were compared to international standard recommended by CIE of 1.08 SED (McKinlay & Diffey, 1987).
METHODOLOGY (cont.) Ethical approval Ethical approval was obtained from the CSIR Research Ethics Committee (Reference number: CSIR REC 642013).
RESULTS
All individual hourly UVR measurements: < 1 SED Daily UVR doses: all farmworkers < 1.7 SED Daily UVR dose: 4 (of 6) farmworkers > 1.08 SED/8 hr CIE standard
RESULTS (cont.) Table 2: Work activities conducted by farmworkers during their workday on 4 June 2014
RESULTS (cont.) 0.50 0.45 0.40 0.35
Worker 1 Worker 2 Worker 3 Worker 4 Worker 5 Worker 6
0.30 0.25 0.20 0.15 0.10 0.05 0.00 08:00 09:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00
Figure 4: Hourly UVR exposure of farmworkers at a farm in Limpopo on 4 June 2014
RESULTS (cont.) 1.80 1.60 1.40 1.20 1.00 0.80 0.60
Daily UV CIE standard /8 hr SED
0.40
0.20 0.00
Figure 5: Total UVR exposure of farmworkers at a farm in Limpopo on 4 June 2014
RESULTS (cont.) 1.00 0.90 0.80 0.70 0.60
0.50 0.40 0.30
Ambient UVR Pretoria Ambient UVR Limpopo Average UVR exposure
0.20 0.10 0.00
Figure 6: Ambient UVR at Pretoria and Limpopo, as well as workers’ average UVR exposure at Limpopo on 4 June 2014
RESULTS (cont.) 70 60 50
Worker 1 Worker 2 Worker 3 Worker 4 Worker 5 Worker 6 Average
40 30 20
10 0 Worker Worker Worker Worker Worker WorkerAverage 1 2 3 4 5 6
Figure 7: Percentage of ambient UVR experienced by workers on 4 June 2014
DISCUSSION
Daily UVR exposure of most workers: exceeded CIE recommended standard (1.08 SED/8 hr) – although it is winter.
However, other researchers: standard very conservative, very easily exceeded (Hammond et al., 2009; Antoine et al., 2007). Hammond et al. (2009): New-Zealand horticulture workers – average UVR exposure of 5.61 SED. Moehrle et al. (2003a): mountain guides – average UVR exceeding recommended standard by factor of six.
DISCUSSION (cont.)
Fitzpatrick skin types V and VI experience sunburn – after continuous UV exposure at levels of 6-10 SED and 10-20 SED respectively (CEN 14255-3, 2008).
All of the farmworkers: types V and VI skin phototype groups.
Sunburn risk not present – no farmworker experienced even a daily dose of > 1.7 SED (much lower that required UVR levels for types V and VI skin).
DISCUSSION (cont.)
Worker 2: highest peak UVR while welding irrigation pipes = added UVR from welding activities?
Added UVR may explain difference in UVR – Worker 2 vs. Worker 5 = assisted in installation of irrigation pipes.
Worker 4: second highest exposure, herding cattle during shift.
Worker 4 higher exposure vs. Worker 1 (also herded cattle) – different work methods = different postures and times spent in shade.
Kimlin et al. (2006) – similar difference: UVR exposure of cyclists.
DISCUSSION (cont.)
Peak average hourly UVR - 12:00 to 13:00.
Farmworkers lunch varied – 13:00 and 14:00 = farmworkers spent lunch time in shade?
Average hourly UVR exposure followed ambient UVR measured at the farm, as well as ambient UVR at Pretoria.
Indicates farmworkers’ personal UVR exposure – greatly influenced by ambient UVR.
DISCUSSION (cont.)
Average percentage of ambient UVR experienced by farmworkers (46 %) – similar to that measured on forearms of Italian farmworkers during winter months (Nardini et al., 2014).
However, Hammond et al. (2009): UVR of approximately 24 % experienced by horticulture workers.
High ambient UVR observed in this pilot study = increased risk in warmer months (i.e. higher ambient UVR).
DISCUSSION (cont.) -
Limitations Conducted during one day in winter. - Further studies: extend sampling period = variations due to weather conditions.
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Number of subjects: restricted to six – number of farmworkers that regularly worked outside. - Future studies: more farms = more subjects.
CONCLUSION
Majority of farmworkers exposed to daily UVR levels in winter that exceeded recommended CIE standard
However, daily doses of UVR lower than in other studies = no indication of an immediate sunburn risk.
High percentage of ambient UVR in winter = potential very high levels of UVR in summer months.
Further studies conducted throughout year = comprehensive representation of farmworkers’ UVR exposure in Limpopo province.
Acknowledgements We would like to thank Dr Martin Allen (University of Canterbury) and Dr Richard McKenzie (NIWA) for lending us the instruments We thank the participants of the study
REFERENCES
AHMED, A.H., SOYER, H.P., SAUNDERS, N., BOUKAMP, P. and ROBERTS, M.S., 2008. Nonmelanoma skin cancers. Drug Discovery Today: Disease Mechanisms, 5(1), pp. e55-e62. ANTOINE, M., SOTTS, P-E., BULLIARD, J-L. and VERNEZ, V. 2007. Effective exposure to solar UV in building workers: influence of local and individual factors. Journal of Exposure Science and Environmental Epidemiology, 17(0), pp. 58-68. CEN (EUROPEAN COMMITTEE FOR STANDARDIZATION). 2008. Measurement and assessment of personal exposure to incoherent optical radiation—part 3: UV-radiation emitted by the sun (Standard No. EN 14255-3:2008). Brussels, Belgium. pp. 32
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REFERENCES (cont.)
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