Carcinogenic metal(loid)s in house dust compared to soil: Concentrations and gastric bioaccessibility.

As a sink and a source of chemicals, house dust represents a relevant medium to assess indoor exposure to metal(loid)s via incidental ingestion or inhalation. However, nationally representative indoor data are scarce. Results from the Canadian House Dust Study (CHDS, 2007-2010; n = 1025) provide nationally representative mean, median and 95 percentile concentrations for 38 elements in typical urban house dust, along with their gastric bioaccessibility.

Identification and quantification of trace metal(loid)s in water-extractable road dust nanoparticles using SP-ICP-MS.

Resuspension of road dust is a major source of airborne particulate matter (PM) in urban environments. Inhalation of ultrafine particles (UFP; < 0.1 μm) represents a health concern due to their ability to reach the alveoli and be translocated into the blood stream.

Viable spores not detected in the household dust of major Canadian cities.

causes infant botulism by colonising the intestines and producing botulinum neurotoxin Previous reports have linked infant botulism cases to spores in household dust, yet the baseline incidence of spores in residential households is currently unknown. Vacuum cleaner dust from 963 households in 13 major Canadian cities was tested for using a novel real-time PCR assay directed against all known subtypes of the botulinum neurotoxin gene. None of the samples tested positive for Analysis of a random subset of samples by MALDI Biotyper revealed that the most common anaerobic bacterial isolates were of the genus and the most common species recovered overall was Dust that was spiked with spores of each toxin type successfully produced positive real-time PCR reactions.

Dissolution Behaviour of Metal-Oxide Nanomaterials in Various Biological Media.

Toxicological effects of metal-oxide-engineered nanomaterials (ENMs) are closely related to their distinct physical-chemical properties, especially solubility and surface reactivity. The present study used five metal-oxide ENMs (ZnO, MnO, CeO, AlO, and FeO) to investigate how various biologically relevant media influenced dissolution behaviour. In both water and cell culture medium (DMEM), the metal-oxide ENMs were more soluble than their bulk analogues, with the exception that bulk-MnO was slightly more soluble in water than nano-MnO and FeO displayed negligible solubility across all tested media (regardless of particle size).

Relationships between House Characteristics and Exposures to Metal(loid)s and Synthetic Organic Contaminants Evaluated Using Settled Indoor Dust.

This study investigates associations between house characteristics and chemical contaminants in house dust, collected under the nationally representative Canadian House Dust Study (2007−2010). Vacuum samples (<80 µm fraction) were analysed for over 200 synthetic organic compounds and metal(loid)s. Spearman rank correlations between contaminant concentrations in dust and presence of children and pets, types of flooring, heating styles and other characteristics suggested a number of indoor sources, pointing to future research directions.

Effect of composting and amendment with biochar and woodchips on the fate and leachability of pharmaceuticals in biosolids destined for land application.

Land application of biosolids can improve soil fertility and enhance crop production. However, the occurrence and persistence of pharmaceutical compounds in the biosolids may result in leaching of these contaminants to surface water and groundwater, causing environmental contamination. This study evaluated the effectiveness of two organic amendments [biochar (BC) and woodchips (WC)] for reducing the concentration and leachability (mobility) of four pharmaceuticals in biosolids derived from wastewater treatment plants in southern Ontario, Canada.

Characterization of Commercial Metal Oxide Nanomaterials: Crystalline Phase, Particle Size and Specific Surface Area.

Physical chemical characterization of nanomaterials is critical to assessing quality control during production, evaluating the impact of material properties on human health and the environment, and developing regulatory frameworks for their use. We have investigated a set of 29 nanomaterials from four metal oxide families (aluminum, copper, titanium and zinc) with a focus on the measurands that are important for the basic characterization of dry nanomaterials and the determination of the dose metrics for nanotoxicology. These include crystalline phase and crystallite size, measured by powder X-ray diffraction, particle shape and size distributions from transmission electron microscopy, and specific surface area, measured by gas adsorption.

Differentiating Inorganics in Biochars Produced at Commercial Scale Using Principal Component Analysis.

Characterizing the inorganic phase of biochar, beyond determining element concentration, is needed for appropriate application of these materials because mineral forms also influence element availability and behavior. Inorganics in 13 biochars (produced from Poultry litter, switchgrass, and different types of wood) were characterized by proximate analysis, chemical analysis, powder X-ray diffraction (XRD), and scanning electron microscopy with energy-dispersive X-ray (SEM-EDX) spectroscopy. Principal component analysis (PCA) was used to compare biochars and characterize associations between elements.

Initial biochar properties related to the removal of As, Se, Pb, Cd, Cu, Ni, and Zn from an acidic suspension.

This study tests the influence of a diverse set of biochar properties on As(V), Se(IV), Cd(II), Cu(II), Ni(II), Pb(II), or Zn(II) removal from solution at pH 4.5. Six commercial biochars produced using different feedstock and pyrolysis conditions were extensively characterized using physical, chemical, and spectroscopic techniques, and their properties were correlated to anion and cation removal using multiple linear regression.

Metal leaching in mine tailings: short-term impact of biochar and wood ash amendments.

Biochar is perceived as a promising amendment to reclaim degraded, metal-contaminated lands. The objective of this study was to compare the potential of biochar and wood ash amendments to reduce metal(loid) leaching in mine tailings. A 2-mo leaching experiment was conducted in duplicate on acidic and alkaline tailings, each mixed with 5 wt.

Zinc in house dust: speciation, bioaccessibility, and impact of humidity.

Indoor exposures to metals arise from a wide variety of indoor and outdoor sources. This study investigates the impact of humid indoor conditions on the bioaccessibility of Zn in dust, and the transformation of Zn species during weathering. House dust samples were subjected to an oxygenated, highly humid atmosphere in a closed chamber for 4 to 5 months.

Chemical transformations of lead compounds under humid conditions: implications for bioaccessibility.

This short communication documents chemical transformations caused by weathering of two Pb compounds that commonly occur in house dust. Chamber experiments were designed to simulate humid indoor environment conditions to determine whether Pb compounds undergo chemical transformations influencing bioaccessibility. Reference compounds of Pb metal (12 % bioaccessibility) and Pb sulfate (14 % bioaccessibility) were subjected to an oxygenated, humidified atmosphere in closed chambers for 4 months.

Lead speciation in house dust from Canadian urban homes using EXAFS, micro-XRF, and micro-XRD.

X-ray absorption fine-structure (XAFS) spectroscopy, micro-X-ray fluorescence (μXRF), and micro-X-ray diffraction (μXRD) were used to determine the speciation of Pb in house dust samples from four Canadian urban homes having elevated Pb concentrations (>1000 mg Pb kg(-1)). Linear combination fitting of the XAFS data, supported by μXRF and μXRD, shows that Pb is complexed in a variety of molecular environments, associated with both the inorganic and organic fractions of the dust samples. The inorganic species of lead identified were as follows: Pb metal, Pb carbonate, Pb hydroxyl carbonate, Pb oxide, and Pb adsorbed to iron oxyhydroxides.

Canadian house dust study: lead bioaccessibility and speciation.

Vacuum samples were collected from 1025 randomly selected urban Canadian homes to investigate bioaccessible Pb (Pb(S)) concentrations in settled house dust. Results indicate a polymodal frequency distribution, consisting of three lognormally distributed subpopulations defined as "urban background" (geomean 58 μg g(-1)), "elevated" (geomean 447 μg g(-1)), and "anomalous" (geomean 1730 μg g(-1)). Dust Pb(S) concentrations in 924 homes (90%) fall into the "urban background" category.

Lead speciation in indoor dust: a case study to assess old paint contribution in a Canadian urban house.

Residents in older homes may experience increased lead (Pb) exposures due to release of lead from interior paints manufactured in past decades, especially pre-1960s. The objective of the study was to determine the speciation of Pb in settled dust from an urban home built during WWII. X-ray absorption near-edge structure (XANES) and micro-X-ray diffraction (XRD) analyses were performed on samples of paint (380-2,920 mg Pb kg(-1)) and dust (200-1,000 mg Pb kg(-1)) collected prior to renovation.

Impact of redox conditions on arsenic mobilization from tailings in a wetland with neutral drainage.

More than 80 years of silver mining in the Cobalt area (Ontario, Canada) has led to widespread contamination of water with arsenic. The objective of this study was to determine the impact of changes in redox conditions on the stability of As in samples collected from a tailings wetland in the historic mining camp. Dissolved metal concentrations were monitored while tailings samples (approximately 1300 mg of As kg(-1), pH 7.

Speciation of hepatic Zn in trout exposed to elevated waterborne Zn using X-ray absorption spectroscopy.

The long-term impacts of chronic metal exposure for aquatic biota are not well understood, partly due to a lack of understanding of metal speciation within tissues. The objective of this study was to determine hepatic Zn speciation of rainbow trout (Oncorhnychus mykiss) exposed to Zn-enriched water in relation to unexposed (control) fish,through direct analysis of freeze-dried liver samples using synchrotron X-ray absorption spectroscopy (XAS). Juvenile rainbow trout (n=30) were exposed to Zn in a two-step process, 200 microg L(-1) for 14 days, followed by 370 microg L(-1) for 23 days.

Speciation of phosphorus in phosphorus-enriched agricultural soils using X-ray absorption near-edge structure spectroscopy and chemical fractionation.

Knowledge of phosphorus (P) species in P-rich soils is useful for assessing P mobility and potential transfer to ground water and surface waters. Soil P was studied using synchrotron X-ray absorption near-edge structure (XANES) spectroscopy (a nondestructive chemical-speciation technique) and sequential chemical fractionation. The objective was to determine the chemical speciation of P in long-term-fertilized, P-rich soils differing in pH, clay, and organic matter contents.