Variability of ambient black carbon concentration in the Central Himalaya and its assessment over the Hindu Kush Himalayan region.

During 2015-2018, eight black carbon (BC) monitoring sites were established in Nepal and Bhutan to fill a significant data gap regarding BC measurement in Central Himalaya. This manuscript analyzes and presents data from these eight stations and one additional station on the Tibetan plateau (TP). Complex topography, varied emission sources, and atmospheric transport pathways significantly impacted the BC concentrations across these stations, with annual mean concentrations varying from 36 ng m-3 to 45,737 ng m-3. Higher annual mean concentrations (5609 ± 4515 ng m-3) were recorded at low-altitude sites than in other locations, with seasonal concentrations highest in the winter (7316 ± 2541 ng m-3). In contrast, the annual mean concentrations were lowest at high-altitude sites (376 ± 448 ng m-3); the BC concentrations at these sites peaked during the pre-monsoon season (930 ± 685 ng m-3). Potential source contributions to the total observed BC were analyzed using the absorption angstrom exponent (AAE). AAE analysis showed the dominance of biomass burning sources (>50 %), except in Kathmandu. By combining our data with previously published literature, we put our measurements in perspective by presenting a comprehensive assessment of BC concentrations and their variability over the Hindu Kush Himalayan (HKH) region. The BC levels in all three geographic regions, high, mid, and low altitude significantly influenced by the persistent seasonal meteorology. However, the mid-altitude stations were substantially affected by valley dynamics and urbanization. The low-altitude stations experienced high BC concentrations during the winter and post-monsoon seasons. Concentration weighted trajectory (CWT) and frequency analyses revealed the dominance of long-range transported pollution during winter over HKH, from west to east. South Asian sources remained significant during the monsoon season. During pre- and post-monsoon, the local, regional, and long-distance pollution varied depending on the location of the receptor site.

Characteristics and Population Size Estimation of Female Sex Workers in Bhutan.

BACKGROUND: Knowing the number of persons at risk for sexually transmitted diseases (STDs) and their risk behaviors are needed to allocate limited resources, set targets for prevention and care activities, gauge the reach of programs, and assess their impact. Female sex workers (FSWs) are a population at high risk for STD worldwide; little is known about FSW in Bhutan. METHODS: We conducted a community-based survey and population size exercise of FSW in Bhutan. The survey used a hybrid venue-based/peer-referral sampling method. Population size estimation methods were key informant mapping, census and enumeration, unique object multiplier, and capture-recapture. RESULTS: Of 517 women surveyed, 67.5% provided sex for money in the last year. Compared with FSWs at venues, FSWs referred by peers were more likely to have sex with alcohol (80.1% vs. 51.5%, P < 0.001) and more paying partners (mean, 3.5 vs. 2.0; P = 0.001), and less likely to have tested for an STD (28.3% vs. 51.0%, P < 0.001) or have outreach worker contact (27.6% vs. 41.5%, P = 0.007). The estimated number of FSWs in the 9 districts was 353 (95% confidence interval, 345-362). Extrapolation to the whole country projected 597 (417-777) FSWs nationally. CONCLUSIONS: Our estimate of the number of FSW in Bhutan corresponds to 0.71% of adult urban women, a figure in line with other countries in South and Southeast Asia. Our data highlight the need for outreach beyond venues where women are employed to reach FSW at higher risk for STD but who have less access to interventions.