the investigation of solar radiation effect on blindness epidemic in the rural areas of chaharmahal and bakhtiari province

1. introduction although solar energy is one of the important renewable, free and clean energy sources, constant exposure to the sun, especially uv radiation, can lead to some problems. these problems include skin diseases, loss of pregnancy, permanent or temporary infertility, and cataracts (strom, 2003), weak immunity system, and an increased risk of diseases especially in children (hoyos-bachiloglu, 2014). cofounding variables such as age, gender, history of diabetes and also, the location of city increase the risk of cataract by 33% (nakashima, 2010). exposure to different qualities of radiation can result in premature diseases impairing the diagnostic power of eye lens cells (blakely, 2010). increased sensitivity to visible light could be determined by the total accumulated dose of radiation during activities (tremsin, 2001). many studies have shown that both psc and cortical opacities are associated with radiation exposure (blakely et al.,2010). cortical cataract has a stronger correlation with exposure to uvr than psc cataract (kanamoto, 2010). chronic exposure to uvr in an interval of three days can lead to promotion of the vulnerability to the eye, but if this time is increased to 30 days, the risk of eye injury is decreased due to the repair of the damaged part (midelfart, 2010). psc and cortical cataract have a stronger correlation with a low dose of space radiation in astronauts, in comparison with the nuclear cataract (chylack, 2010). visual impairment diseases are prevalent in chaharmahal and bakhtiari province. there are 1912 people with various forms of eye diseases. among these, 900 live in rural areas. this study aimed to study the effect of physiographic features and climatic factors on the prevalence of blindness and visual impairment in some rural regions. study area: the villages of chaharmahal and bakhtiari province. 2. material and methods in this study, three sets of data were used: 1. data on the amount of emission radiation and other climatic factors such as sunshine in all stations. 2. the data on visual impairment in 189 rural areas. 3. digital file dem map of chaharmahal and bakhtiari province in the scale of 1:25000 was used to estimate the basis of measurement and the slope in the villages' location and climatic parameters. as the amount of radiation in village location depends on such morphological factors as slope and its orientation and the location of the village, the radiation of the villages was estimated based on village morphological characteristics, using duffy and beckman's (1980) method. because the slope has a significant impact on the intensity of the radiation received at the earth's surface, the amount of it and the villages' slope were calculated based on the topographic map of the province. the villages slope was calculated by the raster map of digital elevation model (dem) in the scale of 1:25000. 3. results and discussion there were 900 blind people in the rural centers, with 547 cases in 57 villages. the percentage in 57 villages was 60.7%, including 30.2% percent of total villages. the highest number was in the south, south east and south west with 256 patients (46.8%) and 45.6% of villages, west and east, with 141 patients (25.8%), and the north, north west and north east, with 150 cases (27.4%), respectively (table 1). the correlation between the slope and the rate of blindness, with r=0.373, was significant. the correlations between slope azimuth to the south and the amount of radiation on slope, and the percentage of increase in the amount of radiation and the slope were r=0.820 and r=0.795, respectively. the village of sar aqa seyyed with high blindness (13.2 in thousands) had a great slope. sheikh ali khan with the highest rate of blindness (49.02 in thousands) also had a southwest slope, which was 14.6 degrees. evaluation of the elevation of the villages showed that all these 57 villages were at altitudes above 1170 meters, and the village of sheikh ali khan with the highest rate of blindness was located at an altitude of 2499 meters above sea level. of the 57 villages, 30 villages with 333 cases of blindness (60%) were at an altitude higher than 2000 meters, 20 villages with 173 cases (31.2 percent) were at an altitude of 1,500 to 2,000 meters, and just 7 villages with 49 cases (8/8 percent) were at an altitude of 1500-1170 meters. in villages with a greater slope, the difference between the red and blue lines was greater. the highest percentage of increase in intensity was in the slopes of the south and south west and south east. generally, the amount of radiation on the slope level was increased by 3.5 percent in all villages. the correlation coefficient between the amount of radiation on the slope level and the percentage of the increase of radiation in the slope level was 0.892. 4. conclusion solar radiation increases the epidemic risk of eye diseases such as cataracts. mountain and high altitudes of chaharmahal and bakhtiari province villages made up the sunshine on slopes facing south, south west and the south east. our study showed that 45.9% of the rural population and 42.1% of villages with a high risk of cataract were in the facing slopes to south and south west and south east. there was a significant relationship between the slope and slope orientation to the south and the rate of blindness. therefore, by increasing the slope and changing slope to the south, the number of cases of blindness was raised in the villages. there was also a significant association between increased height and the increase in the number of villages with blindness and more cases of blindness (60%) lived at an altitude higher than 2,000 meters. because of rise in the highland villages, the height of the atmosphere would be shorter with thinner radiation. there can be, therefore, environmental changes to improve the villages’ microclimatic conditions and reduce the risk of eye disease. for example, by increasing the relative humidity, the sun intensity could be reduced. environmental changes can improve the village microclimatic conditions and reduce the risk of eye disease. thus, by increasing the relative humidity, the air temperature would be reduced; the brightness and intensity of the sun could be reduced and hence, the risk of eye disease would be decreased. better decisions can be them made to change the location or reform the physiographic features of villages needs based on further studies.