Pilot study investigating ambient air toxics emissions near a Canadian kraft pulp and paper facility in Pictou County, Nova Scotia

Climatic conditions and concentrations of BTEX compounds in atmospheric media

Climatic and meteorological conditions are among the factors affecting the ambient concentrations of BTEX compounds. This systematic review and meta-analysis aimed to interrogate the seasonal effect of climatic conditions on the concentrations of BTEX compounds. Three electronic bibliographic databases including Scopus, PubMed, and Web of Science were systematically searched up to November 14, 2023. The search algorithm followed PRISMA guidance and consisted of three groupings of keywords and their possible combinations. For various climatic conditions, the overall mean and 95% confidence interval (CI) of effect size related to BTEX concentrations were calculated using a random-effect model. In total, 104 articles were included for evaluation in this review. BTEX ambient concentration was higher in winter (ranging from 36 out of 79 relevant studies for xylene to 52 out of 97 relevant studies for benzene) followed by summer and autumn. For humidity conditions, the highest exposure values for BTEX were detected for rainy weather (ranging from 3 out of 5 relevant studies for toluene and xylene to 4 out of 5 relevant studies for benzene and ethyl benzene) compared to dry conditions. The pooled concentration (μg/m3) of benzene, toluene, ethyl benzene, and xylene were computed as 2.61, 7.12, 2.21, and 3.61 in spring, 2.13, 7.53, 1.61, and 2.75 in summer, 3.04, 9.59, 3.14, and 5.50 in autumn, and 3.56, 8.71, 2.35, and 3.91 in winter, respectively. Moreover, the pooled concentrations (μg/m3) of BTEX were measured as 2.98, 7.22, 1.90, and 3.03 in dry weather and 3.15, 6.30, 2.14, and 3.86 in rainy or wet weather, respectively. In most seasons, the ambient concentrations of BTEX were higher in countries with low and middle incomes and in Middle Eastern countries and East/Southeast Asia compared to those in other regions (P < 0.001). The increasing concentrations of BTEX in winter and autumn followed by the summer season and during rainy/wet weather appear to be reasonably consistent despite variations in study methods, quality, or geography. Therefore, it is recommended that more serious control measures are considered for decreasing exposure to BTEX in these climatic conditions.

The effects of water, substrate, and intermediate adsorption on the photocatalytic decomposition of air pollutants over nano-TiO2 photocatalysts

The photocatalytic performance of nano-TiO2 photocatalysts in air pollutant degradation greatly depends on the adsorption of water, substrates, and intermediates. Especially under excessive humidity, substrate concentration, and intermediate concentration, the competitive adsorption of water, substrates, and intermediates can seriously inhibit the photocatalytic performance. In the past few years, extensive studies have been performed to investigate the influence of humidity, substrate concentration, and intermediates on the photocatalytic performance of TiO2, and significant advances have been made in the area. However, to the best of our knowledge, there is no review focusing on the effects of water, substrate, and intermediate adsorption to date. A comprehensive understanding of their mechanisms is key to overcoming the limited application of nano-TiO2 photocatalysts in the photocatalytic decomposition of air pollutants. In this review, the progress in experimental and theoretical fields, including a recent combination of photocatalytic experiments and adsorption and photocatalytic simulations by density functional theory (DFT), to explore the impact of adsorption of various reaction components on nano-TiO2 photocatalysts is comprehensively summarized. Additionally, the mechanism and broad perspective of the impact of their adsorption on the photocatalytic activity of TiO2 in air treatment are also critically discussed. Finally, several solutions are proposed to resolve the current problems related to environmental factors. In general, this review contributes a comprehensive perspective of water, substrate, and intermediate adsorption toward boosting the photocatalytic application of TiO2 nanomaterials.

1,3-Butadiene: a ubiquitous environmental mutagen and its associations with diseases

1,3-Butadiene (BD) is a petrochemical manufactured in high volumes. It is a human carcinogen and can induce lymphohematopoietic cancers, particularly leukemia, in occupationally-exposed workers. BD is an air pollutant with the major environmental sources being automobile exhaust and tobacco smoke. It is one of the major constituents and is considered the most carcinogenic compound in cigarette smoke. The BD concentrations in urban areas usually vary between 0.01 and 3.3 μg/m³ but can be significantly higher in some microenvironments. For BD exposure of the general population, microenvironments, particularly indoor microenvironments, are the primary determinant and environmental tobacco smoke is the main contributor. BD has high cancer risk and has been ranked the second or the third in the environmental pollutants monitored in most urban areas, with the cancer risks exceeding 10^-5. Mutagenicity/carcinogenicity of BD is mediated by its genotoxic metabolites but the specific metabolite(s) responsible for the effects in humans have not been determined. BD can be bioactivated to yield three mutagenic epoxide metabolites by cytochrome P450 enzymes, or potentially be biotransformed into a mutagenic chlorohydrin by myeloperoxidase, a peroxidase almost specifically present in neutrophils and monocytes. Several urinary BD biomarkers have been developed, among which N-acetyl-S-(4-hydroxy-2-buten-1-yl)-L-cysteine is the most sensitive and is suitable for biomonitoring BD exposure in the general population. Exposure to BD has been associated with leukemia, cardiovascular disease, and possibly reproductive effects, and may be associated with several cancers, autism, and asthma in children. Collectively, BD is a ubiquitous pollutant that has been associated with a range of adverse health effects and diseases with children being a subpopulation with potentially greater susceptibility. Its adverse effects on human health may have been underestimated and more studies are needed.

A toxicity-based analysis of Canada's National Pollutant Release Inventory (NPRI): a case study in Nova Scotia

After the success of the Toxics Release Inventory (TRI) in the United States (US), Canada created the National Pollutant Release Inventory (NPRI). Both NPRI and TRI focus on public opinion to coerce facilities to reduce quantities of emissions, through market pressure, although early reductions in Canada may be attributed to traditional command-and-control mechanisms. NPRI uses a quantity-based approach to report atmospheric and effluent releases of pollutants to air and water, but does not account for relative toxicity of releases, which could lead to harmful chemicals being overlooked. A toxicity-based approach using characterization factors from the USEtox® environmental impact assessment tool was used for this study. Releases of organic and inorganic pollutants to both air and water in Nova Scotia for 2015 were analyzed. Using an ecotoxicity analysis found that the highest priority chemicals identified using the NPRI's quantity-based approach differed markedly from those identified using the toxicity-based approach. Many of the high-priority chemicals identified using toxicity-based analysis are detrimental to ecosystem health and warrant regulatory attention. The Office of the Auditor General of Canada recently suggested that the Canadian federal government needs to improve control risks of toxic substances. Using a toxicity-based approach may help decision makers in the Canadian federal government effectively control risks of toxic substances and help to inform decision makers, regulators, and Canadians about those risks.

Characterization and spatial distribution of organic-contaminated sediment derived from historical industrial effluents

Organic sediment contaminants [polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans (PCDD/Fs), and polycyclic aromatic hydrocarbons (PAHs)] were assessed using secondary monitoring data from a former tidal estuary (Boat Harbour) impacted by historical industrial effluents. Spatiotemporal characterization of PCDD/Fs and PAHs in sediments was conducted to inform a sediment remediation program designed to return this contaminated aquatic site back to a tidal lagoon. Spatiotemporal variations of sediment PCDD/F and PAH concentrations across Boat Harbour and off-site reference locations were assessed using secondary monitoring data collected between 1992 and 2015. Sediment PCDD/F toxic equivalency (TEQ) and PAH concentrations were compared to sediment quality guidelines. Sediment PCDD/F concentrations exceeded the highest effect thresholds posing severe ecological health risks. High sediment PCDD/F concentrations have persisted in Boat Harbour despite implementation of Pulp and Paper Mill Effluent Chlorinated Dioxins and Furans Regulations in 1992. PAH concentrations varied greatly. Five individual PAH compounds frequently exceeded severe effect thresholds, in contrast to total PAHs, which were below severe effect thresholds. Forensic analysis using PAH diagnostic ratios suggests pyrogenic PAHs derived from wood processes or coal combustion were likely sources. Twenty-five years of monitoring data revealed large data gaps in our understanding of sediment characteristics in Boat Harbour. Gaps included spatial (vertical and horizontal) and temporal variations, presenting challenges for remediation to accurately delineate sediment contaminants. Deeper horizons were poorly characterized compared to shallow sediments (0-15 cm). Historical secondary monitoring data showed that spatial coverage across Boat Harbour was inadequate. Due to severe ecological health risks associated with high sediment PCDD/F concentrations, remediation of the entire sediment inventory is recommended. Detailed vertical and horizontal sampling within Boat Harbour, establishment of local baseline concentrations, and additional sampling in down-gradient-receiving environments for a suite of contaminants are required to better characterize sediments prior to remediation.

A comparison of hourly with annual air pollutant emissions: Implications for estimating acute exposure and public health risk

Health risks from air pollutants are evaluated by comparing chronic (i.e., an average over 1 yr or greater) or acute (typically 1-hr) exposure estimates with chemical- and duration-specific reference values or standards. When estimating long-term pollutant concentrations via exposure modeling, facility-level annual average emission rates are readily available as model inputs for most air pollutants. In contrast, there are far fewer facility-level hour-by-hour emission rates available for many of these same pollutants. In this report, we first analyze hour-by-hour emission rates for total reduced sulfur (TRS) compounds from eight kraft pulp mill operations. This data set is used to demonstrate discrepancies between estimating exposure based on a single TRS emission rate that has been calculated as the mean of all operating hours of the year, as opposed to reported hourly emission rates. A similar analysis is then performed using reported hourly emission rates for sulfur dioxide (SO₂) and oxides of nitrogen (NO_x) from three power generating units from a U.S. power plant. Results demonstrate greater variability at kraft pulp mill operations, with ratios of reported hourly to average hourly TRS emissions ranging from less than 1 to greater than 160 during routine facility operations. Thus, if fluctuations in hourly emission rates are not accounted for, over- or underestimates of hourly exposure, and thus acute health risk, may occur. In addition to this analysis, we also demonstrate an additional challenge when assessing health risk based on hourly exposures: the lack of human health reference values based on 1-hr exposures. Implications: Largely due to the lack of reported hourly emission rate data for many air pollutants, an hourly average emission rate (calculated from an annual emission rate) is often used when modeling the potential for acute health risk. We calculated ratios between reported hourly and hourly average emission rates from pulp and paper mills and a U.S. power plant to demonstrate that if not considered, hourly fluctuations in emissions could result in an over- or underestimation of exposure and risk. We also demonstrate the lack of 1-hr human health reference values meant to be protective of the general population, including children.

Reducing marine pollution from single-use plastics (SUPs): A review

Single-use plastics, or SUPs (plastic bags, microbeads, cutlery, straws and polystyrene) are substantial sources of plastic marine pollution, yet preventable via legislative and non-legislative interventions. Various international legislative strategies have been reported to address plastic marine pollution from plastic bags and microbeads, but these have since been accompanied by recent increasing public awareness triggered by international agencies and organizations. The Sixth International Marine Debris Conference highlighted increasing intervention strategies to mitigate SUP pollution. This study presents new multi-jurisdictional legislative interventions to reduce SUPs since 2017 and incorporates emergence of new non-legislative interventions to mitigate other types of SUPs at individual and private-sector levels that complement or influence legislative interventions. Further, effectiveness of SUP bag interventions (e.g., bans vs. levies) to help reduce SUP marine pollution are presented and range between 33 and 96% reduction in bag use.

The effects of dredging and environmental conditions on concentrations of polycyclic aromatic hydrocarbons in the water column

Sediment dredging can cause damage to the marine environment due to mobilization of sediments and contaminants. The effects of dredging and boundary environmental conditions on the concentration of Polycyclic Aromatic Hydrocarbons (PAHs) in water were evaluated during dredging of the Oil Port of Genoa-Multedo (Italy). Results showed that turbidity and PAH concentrations increased in the water during dredging. However, the scenario was complex due to the high number of interacting physical-chemical factors influencing PAH concentrations and transport. Due to these, PAH distribution is different in water, where low-molecular-weight PAHs were predominant (maximum concentration 0.105 μg L^-1), and in bottom sediments, where high-molecular-weight PAHs had the highest concentrations (from 299.3 to 1256.5 ng g^-1). Moreover, mainly during dredging the PAH concentrations in water were significantly higher inside than outside the port as a consequence of the lower dynamics within the port basin. Turbidity was the main parameter related to PAH concentrations.

Spatiotemporal assessment (quarter century) of pulp mill metal(loid) contaminated sediment to inform remediation decisions

A bleached kraft pulp mill in Nova Scotia has discharged effluent wastewater into Boat Harbour, a former tidal estuary within Pictou Landing First Nation since 1967. Fifty years of effluent discharge into Boat Harbour has created >170,000 m³ of unconsolidated sediment, impacted by inorganic and organic contaminants, including metal[loid]s, polycyclic aromatic hydrocarbons (PAHs), dioxins, and furans. This study aimed to characterize metal(loid)-impacted sediments to inform decisions for a $89 million CAD sediment remediation program. The remediation goals are to return this impacted aquatic site to pre-mill tidal conditions. To understand historical sediment characteristics, spatiotemporal variation covering ~quarter century, of metal(loid) sediment concentrations across 103 Boat Harbour samples from 81 stations and four reference locations, were assessed by reviewing secondary data from 1992 to 2015. Metal(loid) sediment concentrations were compared to current Canadian freshwater and marine sediment quality guidelines (SQGs). Seven metal(loid)s, As, Cd, Cr, Cu, Pb, Hg, and Zn, exceeded low effect freshwater and marine SQGs; six, As, Cd, Cr, Pb, Hg, and Zn, exceeded severe effect freshwater SQGs; and four, Cd, Cu, Hg, and Zn, exceeded severe effect marine SQGs. Metal(loid) concentrations varied widely across three distinct temporal periods. Significantly higher Cd, Cu, Pb, Hg, and Zn concentrations were measured between 1998 and 2000, compared to earlier, 1992-1996 and more recent 2003-2015 data. Most samples, 69%, were shallow (0-15 cm), leaving deeper horizons under-characterized. Geographic information system (GIS) techniques also revealed inadequate spatial coverage, presenting challenges for remedy decisions regarding vertical and horizontal delineation of contaminants. Review of historical monitoring data revealed that gaps still exist in our understanding of sediment characteristics in Boat Harbour, including spatial, vertical and horizontal, and temporal variation of sediment contamination. To help return Boat Harbour to a tidal estuary, more detailed sampling is required to better characterize these sediments and to establish appropriate reference (background) concentrations to help develop cost-effective remediation approaches for this decades-old problem.