Abstract
ObjectivesForest fires in South Asia lead to widespread haze, where many healthy individuals develop psychosomatic symptoms. We investigated the effects of haze exposure on cerebral hemodynamics and new symptoms. We hypothesised that vasoactive substances present in the haze, would lead to vasodilation of cerebral vasculature, thereby altering cerebral hemodynamics, which in turn may account for new psychosomatic symptoms.MethodsSeventy-four healthy volunteers were recruited, and serial transcranial Doppler (TCD) ultrasonography was performed to record blood flow parameters of bilateral middle cerebral arteries (MCA). The first TCD was performed in an air-conditioned environment. It was repeated outdoors after the participants spent 30-minutes in the haze environment. The prevailing level of pollutant standards index (PSI) was recorded. Appropriate statistical analyses were performed to compare cerebral hemodynamics at baseline and after haze exposure in all participants. Subgroup analyses were then employed to compare the findings between symptomatic and asymptomatic participants.ResultsStudy participants’ median age was 30 years (IQR 26–34), and new psychosomatic symptoms were reported by 35 (47.3%). There was a modest but significant decrease in pulsatility index (PI) and resistivity index (RI) in the left MCA after haze exposure (PI: p = 0.026; RI: p = 0.021). When compared to baseline parameters, haze exposure resulted in significantly lower mean PI (p = 0.001) and RI (p = 0.001) in symptomatic patients, but this difference was not present in asymptomatic patients (PI: p = 0.919; RI: p = 0.970).ConclusionHaze causes significant alterations in cerebral hemodynamics in susceptible individuals, probably responsible for various psychosomatic symptoms. The prognostic implications and health effects of haze require evaluation in a larger study.
Highlights
Forest fires from farmers who use the ‘slash-and-burn’ technique for clearing land for agriculture result in seasonal haze that affects large parts of Southeast Asia for several months of the year.[1]
We investigated the effect of acute short-term haze exposure on cerebral hemodynamics in healthy individuals, in addition to the relationship between haze exposure and various psychosomatic symptoms
We demonstrated a negative correlation between mean middle cerebral arteries (MCA) pulsatility index (PI) and the number of psychosomatic symptoms, where the higher the number of psychosomatic symptoms experienced, the Haemodynamic Parameter Baseline
Summary
Forest fires from farmers who use the ‘slash-and-burn’ technique for clearing land for agriculture result in seasonal haze that affects large parts of Southeast Asia for several months of the year.[1] The commonly afflicted countries include Singapore, Malaysia, Thailand and Indonesia These forest fires have been of serious concern in view of their socioeconomic and political impact.[2] During the severe haze crises in 1997 and 2006, estimated economic losses attributable to the haze were US$9 million and US$50 million, respectively.[3, 4] These were largely due to decreased tourism, reduced efficiency in manufacturing and construction (industries involving largely outdoor work), and reduced human productivity (increased sick leave).[5]. Extent of the air pollution correlated with the severity and frequency of symptoms experienced by the exposed population.[7, 8]
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