Current and Future Impacts of Climate Change on Asthma Incidence in Kenya

The linkage between climate change, air quality and human respiratory health was examined in four counties in Kenya. Daily weather observations and satellite air quality measurement for ten years (2004-2013) were used. Daily two-year (2011-2013) hospital admissions records of asthma were used as the predictand. Based on the geoclimatic conditions, Nairobi, Nyeri, Mombasa and Garissa counties were classified as urban, rural, coastal and arid respectively.

A generalized linear model was used to study the relationship between current, multi-day lagged O3, PM2.5, geoclimatic condition, and asthma hospital admissions. This was only possible after adjusting for meteorological variables, nonlinear seasonal effects and day of week effects.From the analysis, it was concluded that all the four geoclimatic conditions (humid coastal, dry arid, moderate urban, and moderate rural), in conjunction with ambient air pollution levels, are associated with increased asthma hospital admissions.

Modeling analyses designed to assess the potential impacts of geoclimatic conditions and air quality on morbidity were then focused into future years. COSMO (Consortium for Small-scale Modeling) model was implemented for the slots 1991-2020 (current) and 2021-2050 (future). The ECHAM4 (European Centre Hamburg Model version 4) model outputs were downscaled to the appropriate resolution needed to characterize the geoclimatic conditions. The outputs were then interfaced with COSMO ART (Aerosols and Reactive Trace gases) Regional Chemistry Transport Model. As was expected, the preliminary agreement with geoclimatic classifications derived from observations was not strong because of the coarse resolution of the ECHAM4 results. The geoclimatic patterns revealed were compared with those based on meteorological observations for the four counties. Good agreement was obtained between the two data sources. This supports the use of the model when characterizing geoclimatic conditions based on future climate scenarios.

Projection results indicate elevated particulate matter concentrations which may lead to a greater likelihood of allergic respiratory disease, upon exposure. However, the limited availability of extensive epidemiological datasets presents lots of uncertainty in making much inference from such association. Areas presently considered rural will observe elevated levels of pollen and could result in new sensitization to asthmatics. This may be attributed to the anticipated changes in environment and land use or long distance transport. Changes in pollen production, allergenicity and geographic distribution of plants may be another attribution for the projected spatial patterns. It is therefore, projected that the nature of these changes may be region specific. In fact the trend in prevalence is decreasing in the coastal region in contrast to the rural and arid areas. On seasonal scale, allergy symptoms may be observed earlier and are likely to last longer. Greater severity from the new allergic cases is also anticipated due to elevated concentrations and subsequent exposure.

From the observed projections, it is concluded that air pollutant concentration and distribution and will be influenced by the anticipated changes to the climate. This in turn, will negatively affect the human respiratory health. Kenya, being one of the Least Developed Countries LDCs and located in Africa will be affected more severely because of its low adaptive capacity.