Comparison between personal sampling methodologies for evaluating diesel particulate matter exposures in mines: submicron total carbon corrected for the adsorption of vapor-phase organic carbon vs. respirable total carbon

In the mining industry, personal measurements of elemental and total carbon are frequently used as surrogates of diesel particulate matter (DPM) exposure, and the respirable or submicron fractions are usually measured. However, vapor-phase organic carbon (OC) can be adsorbed in the filters, interfering with total carbon results. This study presents a comparative evaluation between the submicron fraction of DPM concentrations corrected for the adsorption of the vapor-phase OC (dynamic blank), and the respirable fraction of DPM corrected for a field blank. Respirable and submicron fractions of total carbon (TC_R and TC₁) and elemental carbon (EC_R and EC₁) concentrations were sampled in parallel, in the workers’ breathing zone, in an underground gold mine. A total of 20 full-shift personal samples were taken for each size fraction. Field blanks were collected each day for both the submicron and respirable fractions, while dynamic blank correction was also applied for the submicron fraction. TC_R presented a larger and statistically different geometric mean concentration compared to TC₁ (98 µg/m³ vs. 72 µg/m³; p = 0.01), while the concentrations of EC_R and EC₁ were not statistically different (58 µg/m³ vs. 54 µg/m³; p = 0.74). Average TC_R/EC_R ratio was 1.7, while the TC₁/EC₁ ratio was 1.3. In addition, 93% of EC had an aerodynamic size lower than 1 µm, while the proportion of TC particles in the submicron fraction was lower (73%). Finally, a similar quantity of OC was found when analyzing the dynamic and field blanks of the filters with the submicron fraction selective size (24 µg and 22 µg, respectively). In conclusion, the correction for the vapor phase OC by the dynamic blank was not a significant correction in our study design compared to the field blank samples. This study suggests that the differences in TC may be explained by the different aerodynamic fractions of DPM collected. In addition, elemental carbon measurements did not seem to be extensively affected by the aerodynamic size of the particles collected.     

Determinants of respirable quartz exposure in farming

The objectives of this article are to quantify personal respirable quartz exposure on sandy, sandy loam, and clay soil farms and to identify exposure determinants. The methods applied included observing and examining the variables soil type, commodity farmed, activity, process, quartz % in respirable dust, and weather variables. Multiple linear regression was used to identify determinants of respirable quartz concentration and logistic regression was applied to identify determinants of respirable quartz concentration > 50 µg.m^?3 (a commonly used reference value of over-exposure). The highest quartz concentration was 626 µg.m^?3 and 30%, 22%, and 31% of measurements were > 50 µg.m^?3 for sandy, sandy loam, and clay soil farms, respectively. In general, the commodities livestock farming and cereal grains as well as the activity cereal planter operator, decreased humidity on the day of measurement, the mechanical processes, and quartz % in respirable dust (in a confounding way) were associated with higher respirable quartz concentrations (p ≤ 0.10) as well as season (p = 0.14). Variables associated with quartz levels above 50 µg.m^?3 were cereal planter operator, increased quartz % in respirable dust, decreased humidity on day of measurement, and increased respirable dust concentration. Cereal planter operator (Multivariate Odds Ratio (OR) 4.56, 95% CI: 1.79–8.89) and levels of quartz % > 10 µg.m^?3 (Multivariate OR 6.01, 95% CI: 3.52–9.71 if quartz % > 10 but ≤ 20 µg.m^?3, and Multivariate OR 5.32, 95% CI: 2.56–8.34 if quartz % > 20 µg.m^?3) were clear determinants of quartz over-exposure. It can therefore be concluded that over-exposure to quartz in farming is possible. Joint influences of more farming characteristics and weather variables should be included, together with soil type in future farming exposure assessments.     

Elemental properties of copper slag and measured airborne exposures at a copper slag processing facility

In 1974, the National Institute for Occupational Safety and Health recommended a ban on the use of abrasives containing >1% silica, giving rise to abrasive substitutes like copper slag. We present results from a National Institute for Occupational Safety and Health industrial hygiene survey at a copper slag processing facility that consisted of the collection of bulk samples for metals and silica; and full-shift area and personal air samples for dust, metals, and respirable silica.

Carcinogens, suspect carcinogens, and other toxic elements were detected in all bulk samples, and area and personal air samples. Area air samples identified several areas with elevated levels of inhalable and respirable dust, and respirable silica: quality control check area (236 mg/m³ inhalable; 10.3 mg/m³ respirable; 0.430 mg/m³ silica), inside the screen house (109 mg/m³ inhalable; 13.8 mg/m³ respirable; 0.686 mg/m³ silica), under the conveyor belt leading to the screen house (19.8 mg/m³ inhalable), and inside a conveyor access shack (11.4 mg/m³ inhalable; 1.74 mg/m³ respirable; 0.067 mg/m³ silica). Overall, personal dust samples were lower than area dust samples and did not exceed published occupational exposure limits. Silica samples collected from a plant hand and a laborer exceeded the American Conference of Governmental Industrial Hygienist Threshold Limit Value of 0.025 µg/m³. All workers involved in copper slag processing (n = 5) approached or exceeded the Occupational Safety and Health Administration permissible exposure limit of 10 µg/m³ for arsenic (range: 9.12–18.0 µg/m³). Personal total dust levels were moderately correlated with personal arsenic levels (R_s = 0.70) and personal respirable dust levels were strongly correlated with respirable silica levels (R_s = 0.89).

We identified multiple areas with elevated levels of dust, respirable silica, and metals that may have implications for personal exposure at other facilities if preventive measures are not taken. To our knowledge, this is the first attempt to characterize exposures associated with copper slag processing. More in-depth air monitoring and health surveillance is needed to understand occupational exposures and health outcomes in this industry.     

Measurement of area and personal breathing zone concentrations of diesel particulate matter (DPM) during oil and gas extraction operations,including hydraulic fracturing

Diesel engines serve many purposes in modern oil and gas extraction activities. Diesel particulate matter (DPM) emitted from diesel engines is a complex aerosol that may cause adverse health effects depending on exposure dose and duration. This study reports on personal breathing zone (PBZ) and area measurements for DPM (expressed as elemental carbon) during oil and gas extraction operations including drilling, completions (which includes hydraulic fracturing), and servicing work.

Researchers at the National Institute for Occupational Safety and Health (NIOSH) collected 104 full-shift air samples (49 PBZ and 55 area) in Colorado, North Dakota, Texas, and New Mexico during a four-year period from 2008–2012. The arithmetic mean (AM) of the full shift TWA PBZ samples was 10 µg/m³; measurements ranged from 0.1–52 µg/m³. The geometric mean (GM) for the PBZ samples was 7 µg/m³. The AM of the TWA area measurements was 17 µg/m³ and ranged from 0.1–68 µg/m³. The GM for the area measurements was 9.5 µg/m³. Differences between the GMs of the PBZ samples and area samples were not statistically different (P > 0.05).

Neither the Occupational Safety and Health Administration (OSHA), NIOSH, nor the American Conference of Governmental Industrial Hygienists (ACGIH) have established occupational exposure limits (OEL) for DPM. However, the State of California, Department of Health Services lists a time-weighted average (TWA) OEL for DPM as elemental carbon (EC) exposure of 20 µg/m³. Five of 49 (10.2%) PBZ TWA measurements exceeded the 20 µg/m³ EC criterion. These measurements were collected on Sandmover and Transfer Belt (T-belt) Operators, Blender and Chemical Truck Operators, and Water Transfer Operators during hydraulic fracturing operations.

Recommendations to minimize DPM exposures include elimination (locating diesel-driven pumps away from well sites), substitution, (use of alternative fuels), engineering controls using advanced emission control technologies, administrative controls (configuration of well sites), hazard communication, and worker training.     

Respirable dust and silica exposure among World Trade Center cleanup workers

The cleanup effort following the destruction of the World Trade Center (WTC) was unprecedented and involved removal of 1.8 million tons of rubble over a nine-month period. Work at the site occurred 24 hr a day, 7 days a week and involved thousands of workers during the process. The Occupational Safety and Health Administration (OSHA) conducted personal and area exposure sampling during the cleanup of the site. Secondary data analysis was performed on OSHA air sampling data for respirable dust and silica from September 2001 to June 2002 at the WTC recovery site to characterize workers' exposure. Results for silica and respirable particulate were stratified by area and personal samples as well as job task for analysis. Of 1108 samples included in the analysis, 693 were personal and 415 were area. The mean result for personal silica samples was 42 μg/m³ (Range: 4.2–1800 μg/m³). Workers identified as drillers had the highest mean silica exposure (72 μg/m³; range: 5.8–800 μg/m³) followed by workers identified as dock builders (67 μg/m³; range: 5.8–670 μg/m³). The mean result for personal samples for respirable particulate was 0.44 mg/m³ (range: 0.00010–13 mg/m³). There were no discernable trends in personal respirable dust and silica concentrations with date.     

Respirable crystalline silica exposures during asphalt pavement milling at eleven highway construction sites

Asphalt pavement milling machines use a rotating cutter drum to remove the deteriorated road surface for recycling. The removal of the road surface has the potential to release respirable crystalline silica, to which workers can be exposed. This article describes an evaluation of respirable crystalline silica exposures to the operator and ground worker from two different half-lane and larger asphalt pavement milling machines that had ventilation dust controls and water-sprays designed and installed by the manufacturers.

Manufacturer A completed milling for 11 days at 4 highway construction sites in Wisconsin, and Manufacturer B completed milling for 10 days at 7 highway construction sites in Indiana. To evaluate the dust controls, full-shift personal breathing zone air samples were collected from an operator and ground worker during the course of normal employee work activities of asphalt pavement milling at 11 different sites.

Forty-two personal breathing zone air samples were collected over 21 days (sampling on an operator and ground worker each day). All samples were below 50 µg/m³ for respirable crystalline silica, the National Institute for Occupational Safety and Health recommended exposure limit. The geometric mean personal breathing zone air sample was 6.2 µg/m³ for the operator and 6.1 µg/m³ for the ground worker for the Manufacturer A milling machine. The geometric mean personal breathing zone air sample was 4.2 µg/m³ for the operator and 9.0 µg/m³ for the ground worker for the Manufacturer B milling machine. In addition, upper 95% confidence limits for the mean exposure for each occupation were well below 50 µg/m³ for both studies. The silica content in the bulk asphalt material being milled ranged from 7–23% silica for roads milled by Manufacturer A and from 5–12% silica for roads milled by Manufacturer B.

The results indicate that engineering controls consisting of ventilation controls in combination with water-sprays are capable of controlling occupational exposures to respirable crystalline silica generated by asphalt pavement milling machines on highway construction sites.     

Study on Airborne Heavy Metals in Industrialized Urban Area of Delhi,India

This study assessed the concentrations of airborne heavy metals (HMs) in particulate matter with a cutoff size of 10 µm (i.e., PM₁₀) in an industrialized urban area (Naraina Industrial Area) of New Delhi, India. The samples were collected from January to December, 2011. The annual mean concentrations of selected HMs were as follows As (0.002?±?0.002), Cd (0.030?±?0.020), Co (0.003?±?0.002), Cr (0.170?±?0.081), Cu (0.183?±?0.120), Fe (4.774?±?1.889), Mn (0.258?±?0.145), Ni (0.170?±?0.146), Pb (0.345?±?0.207) and Zn (1.806?±?1.042) µg/m³. The seasonal trend for HMs followed the order postmonsoon?>?winter?>?premonsoon?>?monsoon. Principal component analysis-multiple linear regression (PCA-MLR) suggested the three major emission sources: industrial emission (70?%), mobile and stationary combustion sources (16?%), and suspended/re-suspended dust (14?%). Mean seasonal concentrations of PM₁₀ exceeded both the 24-hour and annual Indian National Ambient Air Quality Standards (NAAQS) of 60 and 100 µg/m³, respectively, in all four seasons. Mean seasonal Ni concentrations in Delhi ambient air also exceeded the 24-h annual NAAQS of 0.020 µg/m³ during all four seasons. Mean Pb concentrations exceeded the annual NAAQS of 0.50 µg/m³ only during the post monsoon season. The high levels of Ni- and Pb-contaminated PM₁₀ would appear to present the possibility of significant health risks.     

Air,hand wipe,and surface wipe sampling for Bisphenol A (BPA) among workers in industries that manufacture and use BPA in the United States

For decades, bisphenol A (BPA) has been used in making polycarbonate, epoxy, and phenolic resins and certain investment casting waxes, yet published exposure data are lacking for U.S. manufacturing workers.

In 2013–2014, BPA air and hand exposures were quantified for 78 workers at six U.S. companies making BPA or BPA-based products. Exposure measures included an inhalable-fraction personal air sample on each of two consecutive work days (n = 146), pre- and end-shift hand wipe samples on the second day (n = 74 each), and surface wipe samples (n = 88). Potential determinants of BPA air and end-shift hand exposures (after natural log transformation) were assessed in univariate and multiple regression mixed models.

The geometric mean (GM) BPA air concentration was 4.0 µg/m³ (maximum 920 µg/m³). The end-shift GM BPA hand level (26 µg/sample) was 10-times higher than the pre-shift level (2.6 µg/sample). BPA air and hand exposures differed significantly by industry and job. BPA air concentrations and end-shift hand levels were highest in the BPA-filled wax manufacturing/reclaim industry (GM_Air = 48 µg/m³, GM_Hand-End = 130 µg/sample) and in the job of working with molten BPA-filled wax (GM_Air = 43 µg/m³, GM_Hand-End = 180 µg/sample), and lowest in the phenolic resins industry (GM_Air = 0.85 µg/m³, GM_Hand-End = 0.43 µg/sample) and in the job of flaking phenolic resins (GM_AIR = 0.62 µg/m³, GM_Hand-End = 0.38 µg/sample). Determinants of increased BPA air concentration were industry, handling BPA containers, spilling BPA, and spending ≥50% of the shift in production areas; increasing age was associated with lower air concentrations. BPA hand exposure determinants were influenced by high values for two workers; for all other workers, tasks involving contact with BPA-containing materials and spending ≥50% of the shift in production areas were associated with increased BPA hand levels. Surface wipe BPA levels were significantly lower in eating/office areas (GM = 9.3 µg/100 cm²) than in production areas (GM = 140 µg/100 cm²).

In conclusion, worker BPA exposure was associated with tasks and conditions affecting both inhalation and dermal exposure. The potential for BPA-related health effects among these workers is unknown.     

Reduction in welding fume and metal exposure of stainless steel welders: an example from the WELDOX study

Purpose

In a plant where flux-cored arc welding was applied to stainless steel, we investigated changes in airborne and internal metal exposure following improvements of exhaust ventilation and respiratory protection.

Methods

Twelve welders were examined at a time in 2008 and in 2011 after improving health protection. Seven welders were enrolled in both surveys. Exposure measurement was performed by personal sampling of respirable welding fume inside the welding helmets during one work shift. Urine and blood samples were taken after the shift. Chromium (Cr), nickel (Ni), and manganese (Mn) were determined in air and biological samples.

Results

The geometric mean of respirable particles could be reduced from 4.1 mg/m³ in 2008–0.5 mg/m³ in 2011. Exposure to airborne metal compounds was also strongly reduced (Mn: 399 vs. 6.8 μg/m³; Cr: 187 vs. 6.3 μg/m³; Ni: 76 vs. 2.8 μg/m³), with the most striking reduction inside helmets with purified air supply. Area sampling revealed several concentrations above established or proposed exposure limits. Urinary metal concentrations were also reduced, but to a lesser extent (Cr: 14.8 vs. 4.5 μg/L; Ni: 7.9 vs. 3.1 μg/L). Although biologically regulated, the mean Mn concentration in blood declined from 12.8 to 8.9 μg/L.

Conclusion

This intervention study demonstrated a distinct reduction in the exposure of welders using improved exhaust ventilation and welding helmets with purified air supply in the daily routine. Data from area sampling and biomonitoring indicated that the area background level may add considerably to the internal exposure.     

Photochemical Production of Atmospheric Carbonyls in a Rural Area in Southern China

For the first time, ambient carbonyls were measured in a rural area in southern China from August 2012 to February 2013 to investigate their distribution characteristics and sources. Formaldehyde, acetaldehyde, and acetone were the three most abundant carbonyls, which accounted for 83–95 % of total seven carbonyls identified. The O₃ formation potential of carbonyls in summer (59.55 μg/m³) was approximately ten times greater than that (6.37 μg/m³) in winter, and calculated photolysis rates were significantly faster in summer than those in winter, suggesting intensive photochemical activities in summer. Seasonal and diurnal variations of carbonyls showed that (1) the concentration of total carbonyls in summer (12.62 ± 10.83 μg/m³) was approximately five times greater than that in winter (2.33 ± 0.90 μg/m³), and a similar trend applied to the three abundant carbonyls; (2) the average summer to winter (S/W) ratio of formaldehyde and acetaldehyde was 10–13, and the S/W ratio of acetone was ~2.59; and (3) the highest concentrations of the three carbonyls and total carbonyls occurred at 14:00–16:00 with high temperature and intensive sunlight, especially in summer. These variations provided direct evidence for significant photochemical production of ambient carbonyls. Average C₁/C₂ ratios (3.07 ± 1.62) in summer were much greater than those (1.28 ± 0.25) in winter, and average C₂/C₃ ratios (35.09 ± 58.67) in summer were significantly greater than those (4.75 ± 2.12) in winter, both cases indirectly implying positive photochemical productions in summer. Especially, strong correlations (R ² = 0.63–0.98) of temperature and sunlight intensity with the three abundant carbonyls and total carbonyls were observed, indicating a similar causal source such as significant photochemical production.     

Long-range fine particulate matter from the 2002 Quebec forest fires and daily mortality in Greater Boston and New York City

During July 2002, forest fires in Quebec, Canada, blanketed the US East Coast with a plume of wood smoke. This “natural experiment” exposed large populations in northeastern US cities to significantly elevated concentrations of fine particulate matter (PM_2.5), providing a unique opportunity to test the association between daily mortality and ambient PM_2.5 levels that are uncorrelated with societal activity rhythms. We obtained PM_2.5 measurement data and mortality data for a 4-week period in July 2002 for the Greater Boston metropolitan area (which has a population of over 1.7 million people) and New York City (which has a population of over 8 million people). Daily average PM_2.5 concentrations were markedly increased for 3 days over this period, reaching as high as 63 μg/m³ for Greater Boston and 86 μg/m³ for New York City from background ambient levels of 4–48 μg/m³ in the non-smoke days. We examined temporal patterns of natural-cause deaths and 24-h ambient PM_2.5 concentrations in July 2002 and did not observe any discernible increase in daily mortality subsequent to the dramatic elevation in ambient PM_2.5 levels. Comparison to mortality rates over the same time periods in 2001 and 2003 showed no evidence of impact. Results from Poisson regression analyses suggest that 24-h ambient PM_2.5 concentrations were not associated with daily mortality. In conclusion, substantial short-term elevation in PM_2.5 concentrations from forest fire smoke were not followed by increased daily mortality in Greater Boston or New York City.     

Associations of short-term exposure to ambient air pollutants with emergency ambulance calls for the exacerbation of essential arterial hypertension

We investigated the association between daily emergency ambulance calls (EAC) for elevated blood pressure that occurred during the time intervals of 8:00–13:59, 14:00–21:59, and 22:00–7:59, and exposure to CO, PM₁₀, and ozone. We used Poisson regression to explore the association between the risk of EAC and short-term variation of pollutants, adjusting for seasonality and weather variables. Before noon, the risk was associated with an interquartile range (IQR) (7.9 μg/m³) increase in PM₁₀ at lag 2–4 days below the median (RR = 1.08, p = 0.031) and with an IQR (0.146 mg/m³) increase in CO at lag 6–7 below the median (RR = 1.05, p = 0.028). During 14:00–21:59, the risk was associated with an IQR (18.8 μg/m³) increase in PM₁₀ on the previous day below the median (RR = 1.04, p = 0.031). At night, EAC were negatively affected by lower O₃ (lag 0–2) below the median (per IQR decrease RR = 1.10, p = 0.018) and a higher PM₁₀ at lag 0–1 above the median for the elderly (RR = 1.07, p = 0.030).     

Occupational Exposure to Crystalline Silica at Alberta Work Sites

Although crystalline silica has been recognized as a health hazard for many years, it is still encountered in many work environments. Numerous studies have revealed an association between exposure to respirable crystalline silica and the development of silicosis and other lung diseases including lung cancer. Alberta Jobs, Skills, Training and Labour conducted a project to evaluate exposure to crystalline silica at a total of 40 work sites across 13 industries. Total airborne respirable dust and respirable crystalline silica concentrations were quite variable, but there was a potential to exceed the Alberta Occupational Exposure Limit (OEL) of 0.025 mg/m³ for respirable crystalline silica at many of the work sites evaluated. The industries with the highest potentials for overexposure occurred in sand and mineral processing (GM 0.090 mg/m³), followed by new commercial building construction (GM 0.055 mg/m³), aggregate mining and crushing (GM 0.048 mg/m³), abrasive blasting (GM 0.027 mg/m³), and demolition (GM 0.027 mg/m³). For worker occupations, geometric mean exposure ranged from 0.105 mg/m³ (brick layer/mason/concrete cutting) to 0.008 mg/m³ (dispatcher/shipping, administration). Potential for GM exposure exceeding the OEL was identified in a number of occupations where it was not expected, such as electricians, carpenters and painters. These exposures were generally related to the specific task the worker was doing, or arose from incidental exposure from other activities at the work site. The results indicate that where there is a potential for activities producing airborne respirable crystalline silica, it is critical that the employer include all worker occupations at the work site in their hazard assessment. There appears to be a relationship between airborne total respirable dust concentration and total respirable dust concentrations, but further study is require to fully characterize this relationship. If this relationship holds true, it may provide a useful hazard assessment tool for employers by which the potential for exposure to airborne respirable silica at the work site can be more easily estimated.     

Hexavalent chromium and isocyanate exposures during military aircraft painting under crossflow ventilation

Exposure control systems performance was investigated in an aircraft painting hangar. The ability of the ventilation system and respiratory protection program to limit worker exposures was examined through air sampling during painting of F/A-18C/D strike fighter aircraft, in four field surveys. Air velocities were measured across the supply filter, exhaust filter, and hangar midplane under crossflow ventilation. Air sampling conducted during painting process phases (wipe-down, primer spraying, and topcoat spraying) encompassed volatile organic compounds, total particulate matter, Cr[VI], metals, nitroethane, and hexamethylene diisocyanate, for two worker groups: sprayers and sprayer helpers (“hosemen”). One of six methyl ethyl ketone and two of six methyl isobutyl ketone samples exceeded the short term exposure limits of 300 and 75 ppm, with means 57 ppm and 63 ppm, respectively. All 12 Cr[VI] 8-hr time-weighted averages exceeded the recommended exposure limit of 1 µg/m³, 11 out of 12 exceeded the permissible exposure limit of 5 µg/m³, and 7 out of 12 exceeded the threshold limit value of 10 µg/m³, with means 38 µg/m³ for sprayers and 8.3 µg/m³ for hosemen. Hexamethylene diisocyanate means were 5.95 µg/m3 for sprayers and 0.645 µg/m³ for hosemen. Total reactive isocyanate group—the total of monomer and oligomer as NCO group mass—showed 6 of 15 personal samples exceeded the United Kingdom Health and Safety Executive workplace exposure limit of 20 µg/m³, with means 50.9 µg/m³ for sprayers and 7.29 µg/m³ for hosemen. Several exposure limits were exceeded, reinforcing continued use of personal protective equipment. The supply rate, 94.4 m³/s (200,000 cfm), produced a velocity of 8.58 m/s (157 fpm) at the supply filter, while the exhaust rate, 68.7 m³/s (146,000 cfm), drew 1.34 m/s (264 fpm) at the exhaust filter. Midway between supply and exhaust locations, the velocity was 0.528 m/s (104 fpm). Supply rate exceeding exhaust rate created re-circulations, turbulence, and fugitive emissions, while wasting energy. Smoke releases showing more effective ventilation here than in other aircraft painting facilities carries technical feasibility relevance.     

BTEX Emissions from the Largest Landfill in Operation in Rio de Janeiro,Brazil

The emission rates and the ambient air concentrations of benzene, toluene, ethyl benzene and xylenes (BTEX) were measured over the intermediate cover layer and atmosphere of the Seropédica landfill, Rio de Janeiro, Brazil. BTEX were sampled using coconut shell charcoal cartridges, followed by extraction with dichloromethane and analysis by gas chromatography with mass spectrometry. Thirteen samples were collected in areas with and without cracks in the cover layer, and six samples were collected from the ambient air. The average emission rates were 11.7, 492.2, 153.7, 67.2, and 21.7 µg m^??2 day^??1, respectively, for benzene, toluene, ethyl benzene, m?+?p-xylenes and o-xylene. No benzene concentrations above the detection limit were observed in ambient air samples. The average concentrations of toluene, ethyl benzene, m?+?p-xylenes and o-xylene in ambient air samples were 2.14, 1.35, 0.49 and 0.08 µg m^??3, respectively. Higher emissions were found in locations containing larger cracks during the collection.     

A preliminary assessment of PM10 and TSP concentrations in Tuticorin, India

The respirable particulate matter (RPM; PM₁₀) and total suspended particulate matter (TSP) concentrations in ambient air in Tuticorin, India, were preliminarily estimated. Statistical analyses on so-generated database were performed to infer frequency distributions and to identify dominant meteorological factor affecting the pollution levels. Both the RPM and TSP levels were well below the permissible limits set by the US Environmental Protection Agency. As expected, lognormal distribution always fit the data during the study period. However, fit with the normal was also acceptable except for very few seasons. The RPM concentrations ranged between 20.9 and 198.2 μg/m³, while the TSP concentrations varied from 51.5 to 333.3 μg/m³ during the study period. There was a better correlation between PM_10–100 and TSP concentrations than that of PM₁₀ (RPM) and TSP concentrations, but the correlation of RPM fraction was also acceptable. It was found that wind speed was the most important meteorological factor affecting the concentrations of the pollutants of present interest. Significant seasonal variations in the pollutant concentrations of present interest were found at 5% significance level except for TSP concentrations in the year 2006.     

Carbonaceous Species of PM<Subscript>2.5</Subscript> in Megacity Delhi,India During 2012–2016

Organic carbon (OC) and elemental carbon (EC) in PM_2.5 were estimated to study the seasonal and inter-annual variability of atmospheric total carbonaceous aerosols (TCA) at an urban site of megacity Delhi, India for 5 years from January, 2012 to December, 2016. The annual average (±?standard deviation) concentrations of PM_2.5, OC, EC and TCA were 128?±?81, 16.6?±?12.2, 8.4?±?5.8 and 34.5?±?25.2 µg m^?3, respectively. During the study, significant seasonal variations in mass concentrations of PM_2.5, OC, EC and TCA were observed with maxima in winter and minima in monsoon seasons. Significant correlations between OC and EC, and OC/EC ratio suggested that vehicular emissions, fossil fuel combustion and biomass burning could be major sources of carbonaceous aerosols of PM_2.5 at the sampling site of Delhi, India.     

Fine particulate matter on hospital admissions for acute exacerbation of chronic obstructive pulmonary disease in southwestern Taiwan during 2006–2012

This study explored the effects of PM_2.5 on hospital admissions (HAs) for acute exacerbation of chronic obstructive pulmonary disease (AECOPD) in southwestern Taiwan. Data on HAs for AECOPD, pollutants, and meteorological variables were obtained from the National Health Insurance Research Database and Environmental Protection Administration. The relative risks (RRs) of HAs for AECOPD was estimated using the Quasi-Poisson generalized additive model. A total of 38,715 HAs for AECOPD were recorded. The average daily HAs for AECOPD and mean 24-h average level of PM_2.5 were 15.2 and 38.8 µg/m³, respectively. For both single and multiple pollutant (adjusted for O₃ and NO₂) models, increased AECOPD admissions were significantly associated with PM_2.5 during cold season, with the RRs for every 10 µg/m³ increase in PM_2.5 being 1.02 (95% CI = 1.007–1.040) at lag 0–1 in single-pollutant, and 1.02 (95 % CI = 1.001–1.042) at lag 0 day in multiple pollutant model. People 65 years of age and older had higher risk of HAs for AECOPD after PM_2.5 exposure. The RRs of PM_2.5 on HAs for AECOPD were robust after adjusting for O₃ and NO₂. Findings reveal an association between PM_2.5 and HAs for AECOPD in southwestern Taiwan, particularly during cold season.     

Atmospheric CO<Subscript>2</Subscript> Level and Temperature Affect Degradation of Pretilachlor and Butachlor in Indian Soil

This study was conducted at ambient (398?±?10 µmol mol^?1), elevated (450?±?10 µmol mol^?1) and elevated (550?±?10 µmol mol^?1) atmospheric CO₂ under three moisture regime and also three level of temperature (4, 25, and 40°C) to assess the degradation of pretilachlor and butachlor. Under dry condition at 398?±?10 µmol mol^?1, T_1/2 was 28.5 and 59.4 days for pretilachlor and butachlor, respectively; slowly decreased to 18.2 and 44.5 days at 550?±?10 µmol mol^?1 indicated that elevated condition enhanced degradation than ambient condition. Under field capacity with increasing CO₂ levels from ambient to elevated, T_1/2 decreased from 18.9 to 11.6 days and 39.4 to 16.2 days for of pretilachlor and butachlor, respectively. Similarly, under submerged conditions with increasing CO₂ levels T_1/2 decreased 14.7–7.1 and 26.3–11.8 days for pretilachlor and butachlor, respectively. Study also revealed that both pretilachlor and butachlor dissipated faster at 40°C (T_1/2, 9.7 and 19.4 days) than 25°C (T_1/2, 16.2 and 36.7 days). Slower dissipation was recorded at 4°C (T_1/2, 87.6 and 182.4 days).