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Ben Gurion University of the Negev (2015)

Dynamics of PM with origins in desert dust : integration of retrospective and prospective analyses with linkage to human health in an arid urban environment

Furman (Krasnov) Helena

Titre : Dynamics of PM with origins in desert dust : integration of retrospective and prospective analyses with linkage to human health in an arid urban environment

Auteur : Furman (Krasnov) Helena

Université de soutenance : Ben Gurion University of the Negev

Grade : Doctor of Philosophy (PhD) 2015

In recent years the role of desert dust storms in the global system has become increasingly apparent. Although many studies on atmospheric particulate matter (PM) have been carried throughout the world, only a few studies have associated PM with origins in desert dust. Nevertheless, the existing PM studies are typically large-scale and restricted to areas where data from monitoring stations are available. In many parts of the world, however, millions of people are exposed to high pollution levels over time. Most of them are living in drylands (arid and semi-arid zones) that are subjected to frequent dust events with limited monitoring systems and dust records. The primary objective of the research was to explore the spatio-temporal dynamics of PM (outdoor and indoor) with origins in desert dust in an urban arid environment (the city of Beer-Sheva, Negev, Israel) with linkage to human health. The Negev is located within the largest global dust belt and experiences several intensive dust storms every year. The unique setting where all the patients are treated by one hospital (Soroka) and one pulmonology clinic allows performing a population based analysis with no subjects lost to follow-up. The first phase of the work was a retrospective analysis of PM10 behavior over time based on data from the last decade and the epidemiological (population based) association to health incidences. The results highlight the high PM10 levels due to dust events. A background value based on the “dust-free” season was used as a threshold value (calculated value = 71 μg m-3 ) to identify potential “dust days.” Subsequently, the net contribution of dust storms to PM10 was assessed (average daily contribution = 122 μg m-3 ). During the study period hourly PM10 concentrations exceeded 5,000 μg m-3 and daily values reach over 2,000 μg m-3 , which is 40 times higher than the WHO guideline (50 μg m-3 ). Based on dust storm intensity parameter (Ai) and temporal analysis, a clear trend of increasing impact of dust storms on PM over the last five years was revealed. This is a major concern for current and future exposure risks that may have a significant effect on human health. A positive association between dust storms and the rate of hospitalization for Chronic Obstructive Pulmonary Disease (COPD) exacerbation among 9,653 patients (IRR=1.16, 95%CI, 1.08-1.24, p<0.001) was found in the studied area. In the second phase, a prospective analysis of PM dynamics (outdoor and indoor) during non-dust days and dust storms was performed with aim to quantify the 14 individual exposures to PM levels. For this purpose, real-time PM2.5 and PM10 levels were measured simultaneously in outdoor and indoor environments throughout the city. The database was constructed using a Geographic Information System to analyze the spatio-temporal distributions of outdoor PM. The results demonstrate that stronger storms increase PM levels in all the city’s neighborhoods. The differences in outdoor PM between different locations can reach as much as 400 µg m-3 , where areas on the windward side of the city will have the highest levels. This allows the identification of "hot spots" where people may be at higher risk. Indoor air quality was also found to be very sensitive to changes in atmospheric PM concentrations during dust events. Indoor PM10 and PM2.5 levels reached very high concentrations of 1,855 µg m-3 and 566 µg m-3 respectively, even when households were protected by closed windows. The determined penetration factor was 0.5 to 0.82 depending on the storm intensity. Thus, indoor exposure risk is critical for health effects. More than 80 patients with COPD or Asthma were enrolled during the second phase. Lung function test showed that mean FEV1FVC (proportion of a person’s vital capacity that they are able to expire in the first second of forced expiration) tend to be lower on average in dust storm days for patients with COPD, but not for Asthma patients. The decrease in lung functions test after the dust storms was found to correlate with high concentrations of indoor PM10. The study addresses major gaps in our knowledge of dust storms especially in arid areas where environmental monitoring is limited, but dust storms are frequent. The findings of this study highlight the impact of dust events on PM and its dynamics in space and time. The outcome of the study can be helpful in creating interventions and policies designed to reduce the exposure risk while enhancing the quality of life in the Negev and other related areas. It is essential to continue to characterize the PM dynamics in space and time in order to better understand its behavior and its various effects on the human environment.

Mots clés : Dust — Environmental aspects — Public health — Israel — Beersheba — Case studies — Airborne infection — Risk assessment — Asthmatics — Health risk assessment — Dust storms — Risk assessment — Lungs — Diseases, Obstructive — Patients — Health risk assessment

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Page publiée le 13 novembre 2016, mise à jour le 21 novembre 2018