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Spatiotemporal exposure modeling of ambient erythemal ultraviolet radiation

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ABSTRACT

Background: Ultraviolet B (UV-B) radiation plays a multifaceted role in human health, inducing DNA damage and representing the primary source of vitamin D for most humans; however, current U.S. UV exposure models are limited in spatial, temporal, and/or spectral resolution. Area-to-point (ATP) residual kriging is a geostatistical method that can be used to create a spatiotemporal exposure model by downscaling from an area- to point-level spatial resolution using fine-scale ancillary data.

Methods: A stratified ATP residual kriging approach was used to predict average July noon-time erythemal UV (UVEry) (mW/m2) biennially from 1998 to 2012 by downscaling National Aeronautics and Space Administration (NASA) Total Ozone Mapping Spectrometer (TOMS) and Ozone Monitoring Instrument (OMI) gridded remote sensing images to a 1 km spatial resolution. Ancillary data were incorporated in random intercept linear mixed-effects regression models. Modeling was performed separately within nine U.S. regions to satisfy stationarity and account for locally varying associations between UVEry and predictors. Cross-validation was used to compare ATP residual kriging models and NASA grids to UV-B Monitoring and Research Program (UVMRP) measurements (gold standard).

Results: Predictors included in the final regional models included surface albedo, aerosol optical depth (AOD), cloud cover, dew point, elevation, latitude, ozone, surface incoming shortwave flux, sulfur dioxide (SO2), year, and interactions between year and surface albedo, AOD, cloud cover, dew point, elevation, latitude, and SO2. ATP residual kriging models more accurately estimated UVEry at UVMRP monitoring stations on average compared to NASA grids across the contiguous U.S. (average mean absolute error [MAE] for ATP, NASA: 15.8, 20.3; average root mean square error [RMSE]: 21.3, 25.5). ATP residual kriging was associated with positive percent relative improvements in MAE (0.6–31.5%) and RMSE (3.6–29.4%) across all regions compared to NASA grids.

Conclusions: ATP residual kriging incorporating fine-scale spatial predictors can provide more accurate, high-resolution UVEry estimates compared to using NASA grids and can be used in epidemiologic studies examining the health effects of ambient UV.

Electronic supplementary material: The online version of this article (doi:10.1186/s12940-016-0197-x) contains supplementary material, which is available to authorized users.

No MeSH data available.


Downscaled average July UVEry from ATP residual kriging models in the contiguous U.S. in 2006
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Fig4: Downscaled average July UVEry from ATP residual kriging models in the contiguous U.S. in 2006

Mentions: Figure 2 shows downscaled average July UVEry predicted from ATP residual kriging separately performed within nine regions across the U.S. biennially from 1998 to 2012. Predicted values ranged between <0 to 390.7 mW/m2 (Fig. 3). Temporal variability in UVEry can be observed in the different geographic distributions of predicted UVEry values across the U.S. year-to-year. As expected, there is a pattern of increasing UVEry values in each year with decreasing latitude moving south towards the Equator. A closer examination of 2006 (Fig. 4) allows for visualization of the spatial variability in predicted UVEry values within the original NASA grids, produced as a result of downscaling from the grid- to finer point-level spatial resolution. Table 2 shows results of the validation comparing UVEry predicted from ATP residual kriging or from NASA grids vs. UVEry observed at UVMRP monitoring stations (Additional file 1: Tables S12–S14 provide detailed validation results by UVMRP station). On average from 1998 to 2012, using ATP residual kriging was associated with a 22.0% relative improvement in MAE and a 16.8% relative improvement in RMSE compared to using NASA grids to predict UVEry observed at the UVMRP monitoring stations. Although the NASA grids provided more accurate UVEry estimates in 2010, MAE and RMSE values were relatively similar when using ATP residual kriging or NASA grids to predict UVEry. There were also regional differences in model predictive performance, where ATP residual kriging provided positive percent relative improvements with respect to MAE and RMSE in each region (Table 3). The largest percent relative improvement in using ATP residual kriging vs. NASA grids to predict UVEry at the UVMRP monitoring stations was observed in the southeast, while the lowest (positive) percent relative improvement was observed in the mid-Atlantic.Fig. 2


Spatiotemporal exposure modeling of ambient erythemal ultraviolet radiation
Downscaled average July UVEry from ATP residual kriging models in the contiguous U.S. in 2006
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5121956&req=5

Fig4: Downscaled average July UVEry from ATP residual kriging models in the contiguous U.S. in 2006
Mentions: Figure 2 shows downscaled average July UVEry predicted from ATP residual kriging separately performed within nine regions across the U.S. biennially from 1998 to 2012. Predicted values ranged between <0 to 390.7 mW/m2 (Fig. 3). Temporal variability in UVEry can be observed in the different geographic distributions of predicted UVEry values across the U.S. year-to-year. As expected, there is a pattern of increasing UVEry values in each year with decreasing latitude moving south towards the Equator. A closer examination of 2006 (Fig. 4) allows for visualization of the spatial variability in predicted UVEry values within the original NASA grids, produced as a result of downscaling from the grid- to finer point-level spatial resolution. Table 2 shows results of the validation comparing UVEry predicted from ATP residual kriging or from NASA grids vs. UVEry observed at UVMRP monitoring stations (Additional file 1: Tables S12–S14 provide detailed validation results by UVMRP station). On average from 1998 to 2012, using ATP residual kriging was associated with a 22.0% relative improvement in MAE and a 16.8% relative improvement in RMSE compared to using NASA grids to predict UVEry observed at the UVMRP monitoring stations. Although the NASA grids provided more accurate UVEry estimates in 2010, MAE and RMSE values were relatively similar when using ATP residual kriging or NASA grids to predict UVEry. There were also regional differences in model predictive performance, where ATP residual kriging provided positive percent relative improvements with respect to MAE and RMSE in each region (Table 3). The largest percent relative improvement in using ATP residual kriging vs. NASA grids to predict UVEry at the UVMRP monitoring stations was observed in the southeast, while the lowest (positive) percent relative improvement was observed in the mid-Atlantic.Fig. 2

View Article: PubMed Central - PubMed

ABSTRACT

Background: Ultraviolet B (UV-B) radiation plays a multifaceted role in human health, inducing DNA damage and representing the primary source of vitamin D for most humans; however, current U.S. UV exposure models are limited in spatial, temporal, and/or spectral resolution. Area-to-point (ATP) residual kriging is a geostatistical method that can be used to create a spatiotemporal exposure model by downscaling from an area- to point-level spatial resolution using fine-scale ancillary data.

Methods: A stratified ATP residual kriging approach was used to predict average July noon-time erythemal UV (UVEry) (mW/m2) biennially from 1998 to 2012 by downscaling National Aeronautics and Space Administration (NASA) Total Ozone Mapping Spectrometer (TOMS) and Ozone Monitoring Instrument (OMI) gridded remote sensing images to a 1&nbsp;km spatial resolution. Ancillary data were incorporated in random intercept linear mixed-effects regression models. Modeling was performed separately within nine U.S. regions to satisfy stationarity and account for locally varying associations between UVEry and predictors. Cross-validation was used to compare ATP residual kriging models and NASA grids to UV-B Monitoring and Research Program (UVMRP) measurements (gold standard).

Results: Predictors included in the final regional models included surface albedo, aerosol optical depth (AOD), cloud cover, dew point, elevation, latitude, ozone, surface incoming shortwave flux, sulfur dioxide (SO2), year, and interactions between year and surface albedo, AOD, cloud cover, dew point, elevation, latitude, and SO2. ATP residual kriging models more accurately estimated UVEry at UVMRP monitoring stations on average compared to NASA grids across the contiguous U.S. (average mean absolute error [MAE] for ATP, NASA: 15.8, 20.3; average root mean square error [RMSE]: 21.3, 25.5). ATP residual kriging was associated with positive percent relative improvements in MAE (0.6&ndash;31.5%) and RMSE (3.6&ndash;29.4%) across all regions compared to NASA grids.

Conclusions: ATP residual kriging incorporating fine-scale spatial predictors can provide more accurate, high-resolution UVEry estimates compared to using NASA grids and can be used in epidemiologic studies examining the health effects of ambient UV.

Electronic supplementary material: The online version of this article (doi:10.1186/s12940-016-0197-x) contains supplementary material, which is available to authorized users.

No MeSH data available.