Development of a high temporal resolution electronic sun journal for monitoring sun exposure patterns

Development of a high temporal resolution electronic sun journal for monitoring sun exposure patterns

Excessive exposure to UV radiation can significantly damage human health. Exposure to UV radiation causes acute effects and long-term effects. Examples of acute effects are sunburn (erythema), immunosuppression and photokeratitis. Long-term effects include melanoma and other skin cancers and ocular disease such as pterygium and cataracts. Measuring personal solar UV exposure and determining sun exposure patterns is important for public health, as more knowledge is needed to define the causes of diseases related to sun exposure. Many studies have employed paper-based sun diaries (journals) or employ expensive electronic dosimeters (which limit the size of the sample population) to estimate periods of exposure.

A cost-effective personal electronic sun journal (ESJ) is developed in this project, which introduces a novel methodology for sensing outdoor exposure patterns. This methodology has not been previously employed for personal solar exposure monitoring. The ESJ was built from a UV infrared photodiode, which was tested in this project to determine if it can be utilised in a personal ESJ, for characterising personal UV exposure patterns. The development of the ESJ was undertaken by testing a group of photodiodes for their physical response. These photodiodes were chosen due to their low cost, their sensitivity to infrared radiation and their cosine response as listed by their manufacturer. The photodiode with the best cosine response was selected to be one of the ESJ circuit elements. The other elements are a 20 kΩ resistor, a 3 V battery and a Tinytag TK-4703 voltage data logger. Preliminary environmental tests were conducted on the ESJ to ensure that it operated correctly and is sensitive to the environment. After the preliminary tests, other tests were performed, including the cosine response test, temperature stability test and sky view test. Environmental characterisation tests were then performed by placing the ESJ in different types of static environments. The ESJ has been used in conjunction with ambient UV meters to estimate the erythemally effective UV exposure. Five individual walking tests, or field trials, were performed, with each trial involving the researcher holding a wooden board with the ESJ and PMA2100 meter and the researcher walking around and through different types of environments with a variety of shade protection. Preliminary environmental test results showed that the ESJ is sensitive to the environment. The temperature stability test showed that the ESJ can be employed in normal summer and winter temperatures. The sky view tests showed that a decrease in sky view leads to an increase in output voltage. Environmental characterisation tests demonstrated the ability of the ESJ to classify the type of environment typically occupied by users. In terms of the characteristics of each tested environment, there was increased output voltage by the ESJ with increasing shade density (reduced sky view). Results of individual walking tests confirmed the ability of ESJ to detect individual exposure patterns.

The greater detail thereby obtained regarding behavioural exposure patterns cannot be obtained by using paper-based sun diaries. Based on the results of this research, the ESJ could replace paper-based sun journals. The latter depend on self-reported volunteer recall, which is subjective and possibly marred by public social desirability bias. The ESJ data offers greater objectivity and could complement existing exposure monitoring in UV research studies for estimating periods of exposure patterns. Using the ESJ further improves the accuracy of long-term epidemiological cumulative exposure studies as high sampling rates can be obtained using this more affordable tool.