The Association Between Personal Air Pollution Exposures and Fractional Exhaled Nitric Oxide (FeNO): A Systematic Review.

PURPOSE OF REVIEW: Airway inflammation is a common biological response to many types of environmental exposures and can lead to increased nitric oxide (NO) concentrations in exhaled breath. In recent years, several studies have evaluated airway inflammation using fractional exhaled nitric oxide (FeNO) as a biomarker of exposures to a range of air pollutants. This systematic review aims to summarize the studies that collected personal-level air pollution data to assess the air pollution-induced FeNO responses and to determine if utilizing personal-level data resulted in an improved characterization of the relationship between air pollution exposures and FeNO compared to using only ambient air pollution exposure data. RECENT FINDINGS: Thirty-six eligible studies were identified. Overall, the studies included in this review establish that an increase in personal exposure to particulate and gaseous air pollutants can significantly increase FeNO. Nine out of the 12 studies reported statistically significant FeNO increases with increasing personal PM2.5 exposures, and up to 11.5% increase in FeNO per IQR increase in exposure has also been reported between FeNO and exposure to gas-phase pollutants, such as ozone, NO2, and benzene. Furthermore, factors such as chronic respiratory diseases, allergies, and medication use were found to be effect modifiers for air pollution-induced FeNO responses. About half of the studies that compared the effect estimates using both personal and ambient air pollution exposure methods reported that only personal exposure yielded significant associations with FeNO response. The evidence from the reviewed studies confirms that FeNO is a sensitive biomarker for air pollutant-induced airway inflammation. Personal air pollution exposure assessment is recommended to accurately assess the air pollution-induced FeNO responses. Furthermore, comprehensive adjustments for the potential confounding factors including the personal exposures of the co-pollutants, respiratory disease status, allergy status, and usage of medications for asthma and allergies are recommended while assessing the air pollution-induced FeNO responses.

Chemical characteristics and oxidative potential of indoor and outdoor PM2.5 in densely populated urban slums.

A significant proportion of population in metropolitan cities in India live in slums which are highly dense and crowded informal housing settlements with poor environmental conditions including high exposure to air pollution. Recent studies report that toxicity is induced by oxidative processes, mediated by the water-soluble PM chemical components leading to reactive oxygen species production thereby causing inflammatory disorders. Hence, for the first time, this study assessed the chemical characteristics and oxidative potential (OP) of indoor and outdoor PM2.5 in two slums in Mumbai, India. Daily gravimetric PM2.5 was measured in ∼40 homes each in a low- and a high-traffic slum and analysed for 18 water-soluble elements and organic carbon (WSOC). Subsequently, OP was assessed through the Dithiothreitol (DTT) assay. Average WSOC was similar in indoor and outdoor environments while the water-soluble concentrations of total elements ranged 4.5-6.5 µg/m3 indoors and 6.4-19.2 µg/m3 outdoors, with S, Ca, K, Na and Zn being the most abundant elements. Spatial distributions of indoor concentrations were influenced by outdoor sources such as local traffic emissions for Cd, Fe, Al and Zn. The influence of outdoor-origin particles was enhanced in homes reporting high air exchange rates. OP was higher outdoors than indoors in both low-traffic slum (0.04-0.51 nmol min-1m-3 outdoors and 0.02-0.38 nmol min-1m-3 indoors) and high-traffic slum (0.03-1.06 nmol min-1m-3 outdoors and 0.04-0.77 nmol min-1m-3 indoors). Outdoor and indoor OP was also more influenced by outdoor road dust showing significant correlation with tracer elements Cu and Al (r ≥ 0.45; p < 0.05). Similar to OP, the non-carcinogenic health risk associated with indoor PM2.5 were also higher in high-traffic slum (Hazard Index, HI = 1.60) than in low-traffic slum (HI = 0.43). Overall, this study shows that the indoor PM2.5 and its chemical constituents in Mumbai slums are primarily of outdoor origin with higher toxicity and non-carcinogenic health risk in high-traffic slums.

Spatial and seasonal variation of outdoor BC and PM2.5 in densely populated urban slums.

A large proportion of residents in urban centers of low- and middle-income countries live in low-socioeconomic neighborhoods called "slums" characterized by low-cost housings of high population density, poor ventilation, and likely poor air quality. This study provides the first quantitative assessment of spatial and seasonal variation of outdoor BC and PM2.5 concentrations in several densely populated slums of Mumbai, India. Mobile outdoor real-time BC and PM2.5 monitoring was conducted along pre-designed monitoring routes in seven slums in Mumbai during the summer (May-June 2015 and May 2016) and repeated in four of them during the winter (February 2016). The measurements were repeated on the routes during different hours and days to account for the temporal variability of air pollution (nsummer = 80 trips; nwinter = 48 trips). PM2.5 exhibited homogenous distribution inside each slum (coefficient of divergence (COD) = 0.11-0.23), while BC varied significantly showing increasing concentrations with proximity to major roads (COD = 0.26-0.64). BC/PM2.5 ratio, an indicator of impact of traffic emissions, was higher along major roads of all slums (14-43%) and minor roads and alleys of high-traffic slums (10-17%) while lowest along alleys and minor roads of low-traffic slums (7-11%). Comparison of pollutant concentrations among major roads revealed the dominant effect of emissions from heavy-duty vehicles and traffic congestion. Significantly high concentrations were observed during winter season compared with summer for both PM2.5 (125 ± 46 µg m-3 in winter and 41 ± 25 µg m-3 in summer) and BC (12 ± 6 µg m-3 in winter and 7 ± 6 µg m-3 in summer). The results of this study indicate that slum residents in Mumbai and similar slums around the world are at a higher risk of traffic-related air pollution, with risk being more severe in winters due to poorer dispersion conditions. Our findings suggest that targeted mitigation strategies to reduce vehicular emissions, especially in high-traffic slums, would yield required benefits.Graphical abstract.

Impending Rupture of Internal Carotid Artery Aneurysm Mimicking Peritonsillar Abscess.

Extracranial carotid artery aneurysms are rare but important entity. Impending rupture of such aneurysms can lead to catastrophic hemorrhage, airway compromise and may prove fatal. The authors report a case of true aneurysm of cervical internal carotid artery in a four-year-old girl who presented with fever and swelling of neck and oropharynx. High clinical suspicion is required to differentiate aneurysm from peritonsillar and parapharyngeal abscess as incision and drainage can prove fatal. Securing airway beforehand and timely embolization has led to the favorable outcome in the present case.