Association between Saharan dust days and emergency hospital admissions in Canary Islands

Abstract

Background The proximity of the Canary Islands to the Northwestern Coast of Morocco (100km) and the regional atmospheric circulation result in an ideal scenario for the transport of African dust from Sahara and Sahel regions towards Canary Islandas. This phenomenon is known as "Saharan dust intrusions". These intrusions can last for one or more days (episodes), reaching occasionally daily average levels higher than 600 ?g/m3 of PM10 and 250 of PM2.5. Aims The aim of this study was to analyze in detail the short-term association between days with Saharan dust intrusions (Saharan dust days, SDD) and morbidity in the cities of Las Palmas de Gran Canaria (LPGC) and Santa Cruz de Tenerife (SCTF) Methods From 2001 to 2005 the association between SDD and daily emergency hospital admissions for respiratory and circulatory diseases was examined using Generalized Additive models adjusting for potential confounders. The effect of concurrent SDD and polynomial distributed lag models [PDLM]) were assessed. Two main types of Saharan dust intrusions over the islands (low and high altitude atmospheric intrusions) were also studied separately Results The number of episodes were 133 in LPGC and 142 in SCTF (561 and 591 SDD respectively). A SDD associated with a 22.6% increase (95% CI 10.4, 36.0) and 29.9% (6.6, 58.4) in risk of all respiratory and COPD admissions respectively in SCTF during the concurrent and the 5 consecutive days. Low altitude atmospheric dust days significantly associated with all respiratory 12.0% (2.7, 22.4) and COPD, 22.7% (4.7, 43.8) in SCTF and with asthma in LPGC: 31.3% (0.9, 70.8). Conclusions We found a short term impact of SDD on emergency hospital admissions for respiratory diseases in both cities that spread over several successive days and that are higher in low altitude atmospheric intrusions. Preventive actions and preparedness plans must be developed for public health protection from these natural events.