Kin Fai Ho

Characteristics and health impacts of VOCs and carbonyls associated with residential cooking activities in Hong Kong.

Cooking emission samples collected in two residential kitchens were compared where towngas (denoted as dwelling A) and liquefied petroleum gas (LPG) (denoted as dwelling B) were used as cooking fuels. A total of 50 different volatile organic compounds (VOCs) were quantified during the 90 min cooking periods. None of any carcinogenic compounds like formaldehyde, acetaldehyde or benzene are detected in the raw fuels, confirming that those are almost entirely derived due to cooking activity alone. Alkenes accounted for approximately 53% of the total measured VOCs collected at dwelling A, while alkanes contributed approximately 95% of the VOCs at dwelling B during the cooking periods. The concentration of aromatic hydrocarbons such as benzene and toluene also increased during the cooking periods. The total amount of carbonyls emitted from the cooking processes at dwelling A (2708 μg) is three times higher than that at dwelling B (793 μg). Acetaldehyde was the most abundant carbonyl at the dwelling A but its emission was insignificant at the dwelling B. Carcinogenic risks on chronic exposure to formaldehyde, acetaldehyde, and benzene for housewives and domestic helpers were evaluated. Formaldehyde accounts for 68% and close to 100% of lifetime cancer risks at dwelling A and B, respectively.

Silica nanoparticles induce autophagy and autophagic cell death in HepG2 cells triggered by reactive oxygen species

Silica nanoparticles (SNPs) are becoming favorable carriers for drug delivery or gene therapy, and in turn, the toxic effect of SNPs on biological systems is gaining attention. Currently, autophagy is recognized as an emerging toxicity mechanism triggered by nanomaterials, yet there have been scarcely research about the mechanisms of autophagy and autophagic cell death associated with SNPs. In this study, we verified the activation of SNPs-induced autophagy via the MDC-staining and LC3-I/LC3-II conversion, resulted in a dose-dependent manner. The typically morphological characteristics (autophagosomes and autolysosomes) of the autophagy process were observed in TEM ultrastructural analysis. In addition, the autophagic cell death was evaluated by cellular co-staining assay. And the underlying mechanisms of autophagy and autophagic cell death were performed using the intracellular ROS detection, autophagy inhibitor and ROS scavenger. Results showed that the elevated ROS level was in line with the increasing of autophagy activation, while both the 3-MA and NAC inhibitors effectively suppressed the autophagy and cell death induced by SNPs. In summary, our findings demonstrated that the SNPs-induced autophagy and autophagic cell death were triggered by the ROS generation in HepG2 cells, suggesting that exposure to SNPs could be a potential hazardous factor for maintaining cellular homeostasis.

Coarse particulate matter associated with increased risk of emergency hospital admissions for pneumonia in Hong Kong.

Background Epidemiological research on the effects of coarse particles (PMc, particulate matter between 2.5 and 10 μm in aerodynamic diameter) on respiratory morbidity is sparse and inconclusive. Pneumonia is an inflammatory condition of lung caused by infections, which may be triggered and exacerbated by PMc exposure. Aim To estimate the effect of PMc on emergency hospital admissions for pneumonia after controlling for PM2.5 and gaseous pollutants. Method PMc concentrations were estimated by subtracting PM2.5 from PM10 measurements in each of the 10 air monitoring stations from January 2011 to December 2012 in Hong Kong and then citywide daily average concentrations of PMc were computed from the 10 stations. Generalised additive Poisson models were used to examine the relationship between PMc and daily emergency hospital admissions for pneumonia, adjusting for PM2.5 and gaseous pollutants (NO2, SO2 and O3). Subgroup analyses by gender and age were also performed to identify the most susceptible subpopulations. Results PMc and PM2.5 were significantly associated with emergency pneumonia hospitalisations. Every 10 μg/m3 increment of PMc in the past 4 days (lag0–lag3) was associated with a 3.33% (95% CI 1.54% to 5.15%) increase in emergency hospitalisations for pneumonia. The effect estimates of PMc were robust to the adjustment of PM2.5, NO2 or SO2, but attenuated on the inclusion of O3 in the model. Women, children and older people might be more vulnerable to PMc exposure. Conclusions Short-term PMc exposure is associated with emergency hospitalisations for pneumonia in Hong Kong. Air quality regulation specifically for PMc might be considered.

Characterization and seasonal variations of levoglucosan in fine particulate matter in Xi’an, China

PM2.5 (particulate matter with an aerodynamic diameter <2.5 μm) samples (n = 58) collected every sixth day in Xi’an, China, from 5 July 2008 to 27 June 2009 are analyzed for levoglucosan (1,6-anhydro-β-d-glucopyranose) to evaluate the impacts of biomass combustion on ambient concentrations. Twenty-four-hour levoglucosan concentrations displayed clear summer minima and winter maxima that ranged from 46 to 1889 ng m−3, with an average of 428 ± 399 ng m−3. Besides agricultural burning, biomass/biofuel combustion for household heating with straws and branches appears to be of regional importance during the heating season in northwestern China. Good correlations (0.70 < R < 0.91) were found between levoglucosan relative to water-soluble K+, Cl−, organic carbon (OC), elemental carbon (EC), and glyoxal. The highest levoglucosan/OC ratio of 2.3% was found in winter, followed by autumn (1.5%). Biomass burning contributed to 5.1–43.8% of OC (with an average of 17.6 ± 8.4%). Implications: PM2.5 levoglucosan concentrations and the correlation between levoglucosan relative to other compounds during four seasons in Xi’an showed that the influence of biomass burning is maximum during the residential heating season (winter), although some important influences may be detected in spring (field preparation burnings) and autumn (corn stalks and wheat straw burning, fallen dead leaves burning) at Xi’an and surrounding areas. Household heating with biomass during winter was quite widespread in Guanzhong Plain. Therefore, the control of biomass/biofuel combustion could be an effective method to reduce pollutant emission on a regional scale.

Physical parameters effect on ozone-initiated formation of indoor secondary organic aerosols with emissions from cleaning products

The effect of air exchange rate (ACH), temperature (T), and relative humidity (RH) on the formation of indoor secondary organic aerosols (SOAs) through ozonolysis of biogenic organic compounds (BVOCs) emitted from floor cleaner was investigated in this study. The total particle count (with D(p) of 6-225 nm) was up to 1.2 × 10(3)#cm(-3) with ACH of 1.08 h(-1), and it became much more significant with ACH of 0.36 h(-1) (1.1 × 10(4)#cm(-3)). This suggests that a higher ventilation rate can effectively dilute indoor BVOCs, resulting in a less ultrafine particle formation. The total particle count increased when temperature changed from 15 to 23 °C but it decreased when the temperature further increased to 30 °C. It could be explained that high temperature restrained the condensation of formed semi-volatile compounds resulting in low yields of SOAs. When the RH was at 50% and 80%, SOA formation (1.1-1.2 × 10(4)#cm(-3)) was the more efficient compared with that at RH of 30% (5.9 × 10(3)#cm(-3)), suggesting higher RH facilitating the initial nucleation processes. Oxidation generated secondary carbonyl compounds were also quantified. Acetone was the most abundant carbonyl compound. The formation mechanisms of formaldehyde and acetone were proposed.

Comparative proteomics of inhaled silver nanoparticles in healthy and allergen provoked mice

Background Silver nanoparticles (AgNPs) have been associated with the exacerbation of asthma; however, the immunological basis for the adjuvant effects of AgNPs is not well understood. Objective The aim of the study reported here was to investigate the allergic effects of AgNP inhalation using proteomic approaches. Methods Allergen provoked mice were exposed to 33 nm AgNPs at 3.3 mg/m3. Following this, bronchoalveolar lavage fluid (BALF) and plasma were collected to determine protein profiles. Results In total, 106 and 79 AgNP-unique proteins were identified in the BALF of control and allergic mice, respectively. Additionally, 40 and 26 AgNP-unique proteins were found in the plasma of control and allergic mice, respectively. The BALF and plasma protein profiles suggested that metabolic, cellular, and immune system processes were associated with pulmonary exposure to AgNPs. In addition, we observed 18 proteins associated with systemic lupus erythematosus that were commonly expressed in both control and allergic mice after AgNP exposure. Significant allergy responses were observed after AgNP exposure in control and allergic mice, as determined by ovalbumin-specific immunoglobulin E. Conclusion Inhaled AgNPs may regulate immune responses in the lungs of both control and allergic mice. Our results suggest that immunology is a vital response to AgNPs.

Seasonal variations of anhydrosugars in PM2.5 in the Pearl River Delta Region, China

Anhydrosugars including levoglucosan and mannosan are the most effective organic tracers for biomass burning aerosol in the atmosphere. In this study, to investigate the contribution of biomass burning emissions to the aerosol burden in the Pearl River Delta (PRD) region, China, 24-hour integrated PM2.5 samples were collected simultaneously at four locations, (i) Guangzhou (GZ), (ii) Zhaoqing (ZQ) in Guangdong province, (iii) Hok Tsui (HT) and (iv) Hong Kong Polytechnic University (PU) in Hong Kong, in four seasons between 2006 and 2007. Levoglucosan and mannosan, together with water-soluble inorganic ions and water-soluble organic carbon (WSOC), were determined to elucidate the seasonal and spatial variations in biomass burning contributions. The concentrations of levoglucosan and mannosan were on average 82.4±123 and 5.8±8.6 ng m−3, respectively. The WSOC concentrations ranged from 0.2 to 9.4 µg m−3, with an average of 2.1±1.6 µg m−3. The relative contributions of biomass burning emissions to OC were 33% in QZ, 12% in GZ, 4% at PU and 5% at HT, respectively, estimated by the measured levoglucosan to organic carbon ratio (LG/OC) relative to literature-derived LG/OC values. The contributions from biomass burning emissions were in general 1.7–2.8 times higher in winter than those in other seasons. Further, it was inferred from diagnostic tracer ratios that a significant fraction of biomass burning emissions was derived from burning of hard wood and likely also from field burning of agricultural residues, such as rice straw, in the PRD region. Our results highlight the contributions from biomass/biofuel burning activities on the regional aerosol budget in South China.

Air pollution and mortality: Effect modification by personal characteristics and specific cause of death in a case-only study

Short-term effects of air pollution on mortality have been well documented in the literature worldwide. Less is known about which subpopulations are more vulnerable to air pollution. We conducted a case-only study in Hong Kong to examine the potential effect modification by personal characteristics and specific causes of death. Individual information of 402,184 deaths of non-external causes and daily mean concentrations of air pollution were collected from 2001 to 2011. For a 10 μg/m(3) increase of pollution concentration, people aged ≥ ∇65 years (compared with younger ages) had a 0.9-1.8% additional increase in mortality related to PM, NO2, and SO2. People dying from cardiorespiratory diseases (compared with other non-external causes) had a 1.6-2.3% additional increase in PM and NO2 related mortality. Other subgroups that were particularly susceptible were females and those economically inactive. Lower socioeconomic status and causes of cardiorespiratory diseases would increase the likelihood of death associated with air pollution.

Estimation of gas-particle partitioning coefficients (Kp) of carcinogenic polycyclic aromatic hydrocarbons in carbonaceous aerosols collected at Chiang-Mai, Bangkok and Hat-Yai, Thailand.

To assess environmental contamination with carcinogens, carbonaceous compounds, water-soluble ionic species and trace gaseous species were identified and quantified every three hours for three days at three different atmospheric layers at the heart of Chiang-Mai, Bangkok and Hat-Yai from December 2006 to February 2007. A DRI Model 2001 Thermal/Optical Carbon Analyzer with the IMPROVE thermal/optical reflectance (TOR) protocol was used to quantify the organic carbon (OC) and elemental carbon (EC) contents in PM10. Diurnal and vertical variability was also carefully investigated. In general, OC and EC mass concentration showed the highest values at the monitoring period of 21.00-00.00 as consequences of human activities at night bazaar coupled with reduction of mixing layer, decreased wind speed and termination of photolysis at nighttime. Morning peaks of carbonaceous compounds were observed during the sampling period of 06:00-09:00, emphasizing the main contribution of traffic emission in the three cities. The estimation of incremental lifetime particulate matter exposure (ILPE) raises concern of high risk of carbonaceous accumulation over workers and residents living close to the observatory sites. The average values of incremental lifetime particulate matter exposure (ILPE) of total carbon at Baiyoke Suit Hotel and Baiyoke Sky Hotel are approximately ten times higher than those air samples collected at Prince of Songkla University Hat-Yai campus corpse incinerator and fish-can manufacturing factory but only slightly higher than those of rice straw burning in Songkla province. This indicates a high risk of developing lung cancer and other respiratory diseases across workers and residents living in high buildings located in Pratunam area. Using knowledge of carbonaceous fractions in PM10, one can estimate the gas-particle partitioning of polycyclic aromatic hydrocarbons (PAHs). Dachs-Eisenreich model highlights the crucial role of adsorption in gas-particle partitioning of low molecular weight PAHs, whereas both absorption and adsorption tend to account for gas-particle partitioning of high molecular weight PAHs in urban residential zones of Thailand. Interestingly, the absorption mode alone plays a minor role in gas-particle partitioning of PAHs in Chiang-Mai, Bangkok and Hat-Yai.

Carbon monoxide and stroke: A time series study of ambient air pollution and emergency hospitalizations

BACKGROUND Recent experimental and clinical studies suggested that exogenous carbon monoxide (CO) at low concentrations may have beneficial neuroprotective effects under certain circumstances. However, population-based epidemiological studies of environmentally relevant CO exposure generated mixed findings. The present study aimed to examine the short-term association of ambient CO with emergency stroke hospitalizations. METHODS A time series study was conducted. Daily air pollution concentrations and emergency hospital admission data from January 2004 to December 2011 in Hong Kong were collected. Generalized additive Poisson models were used to estimate the associations between daily 24-hour mean concentrations of CO and emergency hospital admissions for stroke, while controlling for other traffic related co-pollutants: NO₂ and PM₂.₅. Sensitivity analyses were performed using daily 1-hour maximum concentration of CO as exposure indicator. RESULTS Negative associations were observed between ambient CO concentrations and emergency hospital admissions for stroke. The previous 1-3 day cumulative exposure to CO was associated with a -2.0% (95%CI, -3.3% to -0.7%) decrease in stroke admissions per interquartile range (IQR) increment in CO concentration (0.3 ppm). Similar results were obtained when using 1-hour maximum concentration of CO as exposure indicator. The negative association was robust to the co-pollutant adjustment for either NO₂ or PM₂.₅. Females and elders appeared to be more sensitive to ambient CO exposure. The negative association tended to be larger in cool season. CONCLUSION Short-term exposure to ambient CO was associated with decreased risk of emergency hospitalizations for stroke, suggesting some acute protective effects of CO exposure against stroke onsets.