Evaluation of the health risk of platinum group metals emitted from automotive catalytic converters

Quantifying Platinum and Palladium in Solid Ore Using Laser-Induced Breakdown Spectroscopy Assisted by the Laser-Induced Fluorescence (LIBS-LIF) Technique

The laser-induced breakdown spectroscopy assisted by laser-induced fluorescence (LIBS-LIF) in a two-step process was used to measure the concentration of platinum (Pt) and palladium (Pd) by surface analysis of a solid ore core from the Lac des Iles mine followed by analysis of the same core that was pulverized and compacted. This work focuses mainly on the measurement of Pt since the case of Pd has been extensively discussed in previous work. The excitation of Pt is performed at 235.71 nm with fluorescence emission observed near 269.84 nm. Calibration was performed with synthetic samples prepared from the same ore as the samples studied and the calibration curve shows good linearity in Pt content over several orders of magnitude. A limit of detection (LOD) of approximately 0.15 parts per million (ppm) over an average of 200 laser shots was demonstrated. In contrast, conventional LIBS provides a LOD of about 21 ppm over an average of 200 laser shots due to low signal-to-noise ratio and spectral interference from other elements and does not meet the requirements for estimating the average Pt concentration in the ore. The Pt concentrations obtained using LIBS-LIF on solid ore are generally in good agreement with those obtained in its pulverized and compacted form, as well as with laboratory measurements made by conventional chemical methods. However, the comparison of the results obtained for Pd using LIBS-LIF with the laboratory showed a less satisfactory agreement, probably due to its more inhomogeneous distribution in the ore.

Systemic allergic contact dermatitis to palladium, platinum, and titanium: mechanisms, clinical manifestations, prevalence, and therapeutic approaches

Contact dermatitis (CD) is an inflammatory skin disease of eczema that is elicited by chemicals or metal ions that have toxic effects without eliciting a T-cell response (contact elicitation) or by small reactive chemicals that modify proteins and induce innate and adaptive immune responses (contact allergens). The clinical condition is characterized by localized skin rash, pruritus, redness, swelling, and lesions, which are mainly detected by patch tests and lymphocyte stimulation. Heavy metals such as palladium (Pd), platinum (Pt), and titanium (Ti) are ubiquitous in our environment. These heavy metals have shown CD effects as allergic agents. Immunological responses result from the interaction of cytokines and T cells. Occupational metal CD accounts for most cases of work-related cutaneous disorders. In this systematic review, the allergic effects of heavy metals, including Pd, Pt, and Ti, and the mechanisms, clinical manifestations, prevalence, and therapeutic approaches are discussed in detail. Furthermore, the therapeutic approaches introduced to treat CD, including corticosteroids, topical calcineurin inhibitors, systemic immunosuppressive agents, phototherapy, and antihistamines, can be effective in the treatment of these diseases in the future. Ultimately, the insights identified could lead to improved therapeutic and diagnostic pathways.

Oral and inhalation bioaccessibility of mercury in contaminated soils and potential health risk to the kidneys and neurodevelopment of children in Taiwan

Health risk assessments of exposure to mercury (Hg) from soils via ingestion and inhalation are indispensable for Taiwanese people living in the vicinity of Hg-contaminated sites. In this study, anthropogenic soils were collected from various polluted sources in Taiwan. In vitro oral and inhalation bioaccessible fractions of Hg were analyzed to avoid from overestimating the exposure risk. Discrepancies in oral and inhalation bioaccessible levels of Hg in soils were found using different in vitro assays with different pH levels and chemical compositions. The freshly contaminated soil (soil S7) polluted by chlor-alkali production activity sampled before the site was remediated had the highest total Hg concentration of 1346 mg/kg, with the highest oral bioaccessibility of 26.2% as analyzed by SW-846 Method 1340 and inhalation bioaccessibility of 30.5% as analyzed by modified Gamble's solution. The lesser extent of aging of Hg in soil S7 increased the Hg availability for humans, which was also found based on results of a sequential extraction procedure. Results of the hazard quotient showed that soil ingestion was the main pathway causing non-carcinogenic risks for children and adults. Children were also exposed to higher risks than were adults due to higher frequencies of hand-to-mouth behaviors and lower body weights. Furthermore, hazard index results adjusted for oral and inhalation bioaccessible Hg were lower than those obtained based on the total Hg content; however, an unacceptable value of the non-carcinogenic risk (> 1) for children living near soil S7 was still observed. This study suggests that children living near sites polluted for a short period of time may suffer potential renal effects regardless of the bioaccessibility. Our findings provide suggestions for decision makers on setting new strategies for managing risks of Hg-contaminated soils in Taiwan.

Effects of Platinum Nanoparticles on Rice Seedlings (Oryza sativa L.): Size-dependent Accumulation, Transformation, and Ionomic Influence

Platinum nanoparticles (PtNPs) are increasing in the environment largely due to their wide use and application in automobile and medical industries. The mechanism of uptake behavior of different-sized PtNPs and their association with PtNPs-induced phytotoxicity to plants remains unclear. The present study investigated PtNP uptake mechanisms and phytotoxicity simultaneously to further understand the accumulation and transformation dynamics. The uptake mechanisms were investigated by comparing the uptake and toxicological effects of three different-sized PtNPs (25, 50, and 70 nm) on rice seedlings across an experimental concentration gradient (0.25, 0.5, and 1 mg/L) during germination. The quantitative and qualitative results indicated that 70 nm-sized PtNPs were more efficiently transferred in rice roots. The increase in the PtNP concentration restricted the particle uptake. Particle aggregation was common in plant cells and tended to dissolve on root surfaces. Notably, the dissolution of small particles was simultaneous with the growth of larger particles after PtNPs entered the rice tissues. Ionomic results revealed that PtNP accumulation induced element homeostasis in the shoot ionome. We observed a significant positive correlation between the PtNP concentration and Fe and B accumulation in rice shoots. Compared to particle size, the exposure concentration of PtNPs had a stronger effect on the shoot ionomic response. Our study provides better understanding of the correlation of ionomic change and NP quantitative accumulation induced by PtNPs in rice seedlings.

An improved method for sampling and analytical measurement of aerosol platinum in ambient air and workplace environments

In this study we critically examined with both field and laboratory experiments key components of extant methods for measurement of aerosol soluble platinum in ambient air and workplace environments. Our goal was to develop an improved method for soluble platinum measurement that could be readily implemented in the field and laboratory using readily available modern analytical tools, and in parallel provide insight into factors influencing the robustness of specific aspects of measurement methods for soluble platinum. Experiments addressed sampler type, filter media and pre-cleaning, extraction solvent and volume, extraction time & energy and materials composition, with the objective of optimizing each specific component and promulgating strategies for improving signal/noise and precision. We used basic clean-room protocols and applied ICPMS tools to address these objectives. We document a method that provides for measurement of soluble platinum at the 0.02 ng/m³ level (8-h sample at 2 L/min). Of the four samplers evaluated (IOM, closed-face cassette, and two parallel particle impactors), the IOM exhibited the best precision. The three filter substrates evaluated (Teflon, MCE, PVC) performed similarly in most challenges, however, overall, we conclude that MCE media is the most robust collection substrate for soluble platinum measurements. To achieve the lowest detection levels, it is critical to pre-clean the filter substrates. The use of a 0.07 M HCl extractant (in preference to a water extractant) is recommended - platinum recoveries, particularly from real-world samples, are higher and more consistent with the HCl extractant. The outcomes of the extraction kinetics experiments suggest that an extraction time of 60 min may improve the method performance with 0.07 M HCl but degrade the performance with water, in comparison with a 30-min extraction period. The use of sonication in preference to a table-top shaker is recommended for energy input during extraction.

Immunological Mechanisms of Metal Allergies and the Nickel-Specific TCR-pMHC Interface

Besides having physiological functions and general toxic effects, many metal ions can cause allergic reactions in humans. We here review the immune events involved in the mediation of metal allergies. We focus on nickel (Ni), cobalt (Co) and palladium (Pd), because these allergens are among the most prevalent sensitizers (Ni, Co) and immediate neighbors in the periodic table of the chemical elements. Co-sensitization between Ni and the other two metals is frequent while the knowledge on a possible immunological cross-reactivity using in vivo and in vitro approaches remains limited. At the center of an allergic reaction lies the capability of a metal allergen to form T cell epitopes that are recognized by specific T cell receptors (TCR). Technological advances such as activation-induced marker assays and TCR high-throughput sequencing recently provided new insights into the interaction of Ni2+ with the αβ TCR-peptide-major histocompatibility complex (pMHC) interface. Ni2+ functionally binds to the TCR gene segment TRAV9-2 or a histidine in the complementarity determining region 3 (CDR3), the main antigen binding region. Thus, we overview known, newly identified and hypothesized mechanisms of metal-specific T cell activation and discuss current knowledge on cross-reactivity.

Risks and phyto-uptake of micro-nano size particulates bound with potentially toxic metals in Pb-contaminated alkaline soil (NW China): The role of particle size fractions

The fate and risk in the environment of potentially toxic metals (PTMs) pollutants depends on the size-fractions of contaminated soil. In this study, the variable micro-nano size-fractions of 50-250 μm, 5-50 μm, 1-5 μm, <1 μm in long-term Pb-contaminated alkaline soil (NW China) were obtained by Sequential Wet Sieving Separation Procedure (SWSSP). The chemical speciation, mobility and risk of PTMs in micro-nano particle fractions as well as their uptaken and translocation in Maize (Zea mays L.) plant were systematically determined. The results demonstrated that higher accumulation of both investigated PTMs was observed in the fine fractions of <1 μm. The metallic Pb predominantly occurred in all size-fractions (65%-86%) identified by XPS, and the reducible forms of lead oxide (Ⅱ,Ⅳ) would also likely preferred to enrich in the fine fraction of <1 μm. The mobility and bioaccessibility of PTMs in fine fraction of <1 μm were higher than other fractions, which were identified by the multi-indices, enrichment factor (EF), accumulation factor (AF), mobility factor (MF), potential ecological risk index of single metal (E_rⁱ) and the comprehensive potential ecological risk index (RI). The scenario for phyto-uptake of Pb and Cu in <1 μm soil nanoparticles under pot tests indicated that the Pb and Cu enriched in <1 μm with high ecological risk were inclined to translocate into the Maize roots and shoots with nano size fractions. The results implied that further environmental management should be needed in order to prevent the risk of PTMs from Pb-bearing micro-nano size fractions in the industrial contaminated alkaline soil.

A Weight-of-the-Evidence Approach for Evaluating, in Lieu of Animal Studies, the Potential of a Novel Polysaccharide Polymer to Produce Lung Overload

The United States Environmental Protection Agency (EPA) is concerned about the respiratory effects caused by respirable particles of water-insoluble high molecular weight polymers. The EPA has proposed a tiered approach to evaluate polymer lung overload, a kinetic event. Kinetic polymer lung overload in itself is not necessarily adverse, however, inhalation of respirable particulate matter can have adverse effects (i.e., inflammation, fibrosis, etc.). If Tier I testing demonstrates that particles may reach the distal lung (i.e., a non-negligible amount of respirable particles/droplets ≤10 μm in diameter and lack of biosolubility), then animal inhalation testing in Tiers II-IV would be requested. In silico, in chemico, and in vitro alternatives should be considered versus in vivo testing for animal welfare purposes. An in chemico measure of biosolubility was used to demonstrate that a novel α-1,3-glucan polysaccharide, made by enzymatic polymerization of glucose from sucrose, is biosoluble and fits a simple exponential decay model with a half-life on the order of 66 days. The multiple-path particle dosimetry (MPPD) in silico model was used to predict lung burden for the novel α-1,3-glucan polysaccharide. MPPD was validated with measurements in rats exposed to a toner particulate and showed good agreement with lung burden measurements. A simulated 24 month rat exposure yielded 10-20 times less lung burden for the polysaccharide compared to the toner at equivalent exposure concentrations. The MPPD model was refined to include biosolubility data for the polysaccharide polymer. Data for amorphous silica were used to validate the clearance model, and the model incorporating dissolution predicted the amorphous silica lung burden within 20% of measured values. Human equivalent concentrations (HECs) were calculated for each toner rat exposure concentration. HECs were also determined for the polysaccharide at exposure concentrations yielding the same predicted internal doses as the toner. The in vitro, in chemico and in silico studies described here for the novel polysaccharide provide a useful weight of evidence approach in the absence of animal studies for the evaluation of polymer substances where polymer lung overload may be a concern.

Zero-valent palladium dissolution using NaCl/CuCl2 solutions

Pd, Rh, Pt are employed in a wide range of applications, such as catalytic converters, fuel cells and electronic devices. In the last years, an increasing pressure on their market was recorded due to a growing demand and limited resources. Therefore, the recovery of these materials from wastes represents an interesting goal to be achieved. The most widely proposed techniques for recovering the palladium from wastes are leaching and ion exchange. Strong oxidizers, acids and high temperature (343-363 K) are used for leaching, leading problems for the environment and the safety. In this work the attention was focused on a system containing zero-valent palladium nanoparticles in which the leaching is performed in mild acidic conditions, by using chloride solutions containing cupric ions (NaCl/CuCl₂). The process was studied at varying temperature, pH, chloride and cupric ion concentrations. Good results were obtained at pH 5.0 and temperatures between 288 K and 333 K. The process is more acceptable than the traditional ones from a safety point of view being characterized by less severe conditions (pH and temperatures). A shrinking spherical particles model was adopted to analyse the experimental data from which a development under a kinetic control was demonstrated.

Improving the regulatory health risk assessment of mercury-contaminated sites

An alternative risk assessment strategy for mercury (Hg)-contaminated sites is proposed with bioaccessible fractions and soil Hg vapor (SHgV) concentrations. The new strategy avoids the conservatism of assessment rely on soil total Hg (THg) content and inaccuracy caused by predicted SHgV concentration. The exposure risk to Hg-contaminated soil associated with historical mining activities in Guizhou, China, was evaluated using the proposed strategy. The experimental results revealed that the average bioaccessibility in gastric, intestinal and lung phases was 10.39 % (2.09 % ∼ 35.28 %), 1.28 % (0.23 % ∼ 4.3 %), and 11.27 % (5.04 % ∼ 20.71 %), respectively. Via the proposed strategy, the Hg risk for the oral ingestion pathway, represented as the hazard quotient (HQ), decreased from 1.57 to an acceptable level of 0.19 (<1). The risk of SHgV inhalation sharply decreased from 1168 to 0.35 while the soil PM₁₀ inhalation pathway did not exhibit significant variations. The dominant exposure pathways turned to oral intake and inhalation of SHgV by the strategy. The results indicated that the proposed assessment strategy can greatly improve the understanding of the exposure risk level at Hg-contaminated sites and provide a reasonable decision basis for decision makers.

Comparative study on a kilowatt-MPT-MS-based method with two ion polarity modes for the inert palladium metal

Inert metals are of much importance and play a key role in modern industrial manufacturing. The analytical techniques of inert metals remain challenging. In particular, the mass spectrometry of inert metal elements is yet to be further developed, which also limits the contemporary conceptual in situ analysis of inert metals. As the representative element, the mass spectral detection of palladium is critical and of far-reaching significance. Herein, we developed a mass spectrometry method, which can be used for the high-speed and in situ analysis of palladium, and even for other inert metals. Combining the line ion trap mass spectrometer with the versatile ambient ionization source, a novel kilowatt microwave plasma torch (MPT) can be used to obtain the fully characteristic MPT mass spectra of palladium. Detailed multistage tandem mass spectra show that the general form of target ions is [M(O2)x(NO)mNy(NO2)n]- for the negative ion mode and [M(H2O)x(NO2)y(N2)m]+ for the positive ion mode. Moreover, the formation and evolution of these palladium complex ions were reasonably derived based on the analysis of MPT background mass spectra. This mass spectrometric technique is also suitable for the determination of the palladium-containing solution in the sub-trace level. Semi-quantitative results showed that the detecting ability for palladium in the negative mode is better than that of the positive mode. Under the negative ion mode, the limit of detection (LOD) for m/z 259 were evaluated to be 0.5 μg L-1 under the optimized conditions of the negative mode, with the linear range of 1-100 μg·L-1 (R2 ≥ 0.9985) and the relative standard deviation (RSD, n = 11) being in the range of 1.20%-5.98% (refer to Table S3). Our experimental data showed that MPT-MS was a promising technique for providing another alternative in the on-site analysis of liquid samples and other intimate relevant fields, as the supplement of ICP-MS for the detection of inert metal elements. On the other hand, this work will also certainly promote the more broad applications of platinum-group elements (PGE) in modern science and industry.

Urban Soils and Road Dust—Civilization Effects and Metal Pollution—A Review

Urban soils have been changed much by human impacts in terms of structure, composition and use. This review paper gives a general introduction into changes from compaction, mixing, water retention, nutrient inputs, sealing, gardening, and pollution. Because pollutions in particular have caused concerns in the past, metal pollutions and platinum group metal inputs have been treated in more detail. Though it is not possible to cover the entire literature done on this field, it has been tried to give examples from all continents, regarding geochemical background levels. Urban metal soil pollution depends on the age of the settlement, current emissions from traffic and industry, and washout. It seems that in regions of high precipitation, pollutants are swept away to the watershed, leaving the soils less polluted than in Europe. Health hazards, however, are caused by ingestion and inhalation, which are higher in 3rd world countries, and not by concentrations met in urban soils as such; these are not treated within this paper in detail. With respect to pollutants, this paper is focused on metals. Contrary to many reviews of the past, which mix all data into one column, like sampling depth, sieved grain sizes, digestion and determination methods, these have been considered, because this might lead to considerable interpretation changes. Because many datasets are not Gaussian distributed, medians and concentration ranges are given, wherever possible. Urban dust contains about two to three fold the hazardous metal concentrations met in urban soils. Some data about metal mobilities obtained from selective and sequential leaching procedures, are also added. Soil compaction, pollution, sealings and run-offs cause stress situations for green plants growing at roadside locations, which is discussed in the Section 5. Environmental protection measures have led to decrease metal pollutions within the last decade in many places.

In vitro lung and gastrointestinal bioaccessibility of potentially toxic metals in Pb-contaminated alkaline urban soil: The role of particle size fractions

Potentially toxic metals (PTMs), associated with different size particles in soil, may play an important role in adverse health effect and risk for human. The objective is to evaluate the lung and gastrointestinal bioaccessibility and risk of PTMs in Pb-contaminated alkaline urban soil depending on the particle size fractions. The size fractions of 50-250 μm, 5-50 μm, 1-5 μm, <1 μm in Pb-contaminated alkaline urban soil from Baoji Heavy Industrial Base City, NW China, were screened by Sequential Wet Sieving Separation Procedure (SWSSP) based on Stokes' Law. The concentrations of 9 potentially toxic metals (As, Ba, Co, Cr, Cu, Mn, Ni, Pb and Zn) in each particle size fractions were characterized by ICP-OES and ICP-MS, and the in vitro bioaccessibility dependent of size fractions were evaluated by the simulation fluids of Artificial Lysosomal Fluid (ALF) and Gamble for lung, PBET, SBET, IVG, SBRC, UBM for gastric and intestinal, respectively. Health risks were assessed considering simulated external exposure using intestinal and lung bioaccessibility. The lung and gastrointestinal bioaccessibility and exposure risks of PTMs in fine particle size (i.e. <1 μm) was higher than larger particle size fractions (i.e. 50-250 μm, 5-50 μm, 1-5 μm), however, some different variations of bioaccessibility observed the simulation fluids and time dependent. In case of single PTMs, the lung bioaccessibilities of PTMs in ALF were higher than those in Gamble fluids, most prominent in Co, Cu, Mn and Zn, while the gastrointestinal [G + I] bioaccessibility of PTMs was less than those in gastric [G], like Cu, Mn, Pb and Zn mostly. The non-carcinogenic risks of these PTMs to children via inhalation were acceptable and higher than those of adults, but reverse for carcinogenic risk. Comparatively, the non-carcinogenic and carcinogenic risks of PTMs via ingestion pathway were both higher than those for adults. Although the risks from ingestion were in acceptable range, the total carcinogenic risks for children were more than 10^-4, which would bring carcinogenic risks and should be paid attention to. It was noted that the toxic metal, Co in all size fractions was the most important contributor for noncarcinogenic risks and Cr mostly for carcinogenic risks via inhalation pathway for adults and children in local areas. However, Pb was the most important contributor for noncarcinogenic risk both for adults and children via ingestion pathway relative to Co and Cr for carcinogenic risks through hand-to-mouth ingestion. Those observations demonstrated the important role that the smaller particle fractionations in Pb-contaminated alkaline soil played in both bioaccessibility and the refinement of human health-risk assessments for the inhalation and ingestion pathway.

Recent advances in three-way catalysts of natural gas vehicles

This review presents recent advances in TWCs for NGVs, particularly for Pd-based catalysts and potential alternatives.

Adsorption and fractionation of Pt, Pd and Rh onto inorganic microparticles and the effects of macromolecular organic compounds in seawater

Adsorption and fractionation of Pt, Pd and Rh (defined here as platinum group elements, PGEs) onto the representative inorganic microparticles, including Fe₂O₃, MnO₂, CaCO₃, SiO₂, Al₂O₃ and kaolinite in seawater were investigated. The effects of macromolecular organic compounds (MOCs) as the representatives of organic matter, including humic acids (HA), bovine serum albumin (BSA) and carrageenan, on the adsorption were also studied considering that organic matter is ubiquitous in seawater and indispensable to marine biogeochemical cycles. In the absence of MOCs, the representative mineral particles Fe₂O₃ and MnO₂ had the strongest interaction with PGEs. The adsorption of PGEs onto the representative biogenic particles SiO₂ and CaCO₃ and lithogenic particles Al₂O₃ and kaolinite was similar or weaker than onto the mineral particles. MOCs inhibited the interaction between PGEs and the particles except for Pt and Pd onto the biogenic particles in artificial seawater. This impediment may be closely related to the interaction between particles, MOCs and elements. The partition coefficient (log K_d) of Pt was similar (∼4.0) in the presence of MOCs, indicating that the complexation between Pt and MOCs was less important than hydrolysis or adsorption onto the acid oxide particle surface. Rh tended to fractionate onto the mineral and lithogenic particles in the presence of HA and carrageenan, while Pd was more likely to fractionate onto the biogenic particles. However, BSA enhanced the fractionation tendency of Pd onto the mineral particles. The results indicate that the adsorption behavior of Pd onto inorganic particles was significantly affected by the composition or the type of MOCs. Hence, the interaction between PGEs and inorganic particles may be greatly affected by the macromolecular organic matter in the ocean.

A porous organic polymer with magnetic nanoparticles on a chip array for preconcentration of platinum(IV), gold(III) and bismuth(III) prior to their on-line quantitation by ICP-MS

A chip-based array is described for magnetic solid-phase microextraction (MSPME) of the ions of Pt, Au and Bi. Magnetic porous organic polymers (MOPs) prepared from magnetite nanoparticles and 1,3,5-tris(4-aminophenyl)benzene are introduced as a novel adsorbent. Eight solid phase extraction columns packed with MOPs were integrated in parallel on a microfluidic chip for array microextraction. After elution with a 12% (m/v) solution of cysteamine hydrochloride (pH 8.0), the eluent is introduced into an ICP-MS instrument for quantification. Under the optimized conditions, the limits of detection for Pt, Au and Bi are 8.6, 4.4 and 3.4 ng L^-1, respectively. The sample throughput is 7 h^-1, and the adsorption capacities are 32, 24 and 24 μg mg^-1 for Pt, Au and Bi, respectively. The method was validated by the determination of Bi in a certified reference material (GSH-1A; human hair), and the values obtained coincided with the certified value. This method was also applied to the determination of Pt, Au and Bi in (spiked) urine and cell samples, and good recoveries (85.8-113%) were achieved. The method is highly sensitive and has a high throughput and a low sample/reagent consumption (with 500 HeLa cells consumed). Graphical abstract Schematic presentation of the magnetic packed column, microfluidic chip, and online chip-based MSPME-ICPMS system. Design sketch of the online system: microextraction unit (blue lines), microvalves (black lines), outlet channels (yellow lines), permanent magnets (red), urine and cell samples.

An assessment of the inhalation bioaccessibility of platinum group elements in road dust using a simulated lung fluid

Metal enrichment of road dust is well characterized but available data on the bioaccessibility of metals in particle size fractions relevant to human respiratory health remain limited. The study goal was to investigate the bioaccessibility of platinum group elements (PGE), which are used as catalysts in automotive exhaust converters, in the inhalable fraction of road dust. Street sweepings were provided by the City of Toronto, Canada, collected as part of its Clean Roads to Clean Air program.The particle size relevance of road dust for inhalation exposures was confirmed using a laser diffraction particle size analyzer (mean Dx(50): 9.42 μm). Total PGE were determined in both bulk and inhalable fractions using nickel sulfide (NiS) fire-assay and instrumental neutron-activation analysis (INAA). PGE lung solubility was examined for the inhalable fraction using Gamble's extraction. Sample digests were co-precipitated with Te-Sn, to pre-concentrate and isolate PGE, prior to their measurement using inductively coupled plasma mass spectrometry (ICP-MS).Total PGE concentrations were enriched in the inhalable fraction of road sweepings. Geomean concentrations in the inhalable fraction were: palladium (Pd) (152 μg/kg), platinum (Pt) (55 μg/kg), rhodium (Rh) (21 μg/kg) and iridium (Ir) (0.23 μg/kg). Osmium (Os) concentrations were below the limit of detection (LOD). Bioaccessible PGEs (n = 16) using Gamble's solution were below LOD for Ir and ruthenium (Ru). For the remainder, the geomean % bioaccessibility was highest for platinum (16%), followed by rhodium (14%) and palladium (3.4%). This study provides evidence that PGE in road dust are bioaccessible in the human lung.

Preparation of Palladium(II) Ion-Imprinted Polymeric Nanospheres and Its Removal of Palladium(II) from Aqueous Solution

Three kinds of functional monomers, 4-vinylpridine(4-VP), 2-(allylthio)nicotinic acid(ANA), and 2-Acetamidoacrylic acid(AAA), were used to synthetize palladium(II) ion-imprinted polymeric nanospheres (Pd(II) IIPs) via precipitation-polymerization method in order to study the effects of different functional monomers on the adsorption properties of ion-imprinted materials. The results of UV spectra in order to study the interaction between template ion PdCl₄^2- and functional monomers showed that there were great differences in structure after the template reacted with three functional monomers, 4-VP and ANA caused a large structural change, while AAA basically did not change. Further results on the adsorption performance of Pd(II) IIPs on Pd(II) confirmed 4-VP was the most promising candidate for the synthesis of Pd(II) IIPs with an adsorption capacity of 5.042 mg/g as compared with ANA and AAA. The influence of operating parameters on Pd(II) IIP's performance on Pd(II) adsorption was investigated. There was an increase in the adsorption capacity of Pd(II) IIPs at higher pH, temperature, and initial concentration of Pd(II). The results of multi-metal competitive adsorption experiments showed that Pd(II) IIPs had selectivity for Pd(II). An adsorption equilibrium could be reached at 180 min. Kinetic analysis showed that the adsorption test data fitted best to the pseudo-second order kinetic model, and the theoretical equilibrium adsorption capacity was about 5.085 mg/g. The adsorption isotherms of Pd(II) by Pd(II) IIPs agreed well with the Freundlich equation, suggesting a favorable adsorption reaction under optimal conditions. These results showed that Pd(II) IIPs have potential application in the removal of Pd(II) from aqueous solutions and may provide some information for the selection of functional monomers in the preparation of Pd(II) IIPs.

Lung bioaccessibility of As, Cu, Fe, Mn, Ni, Pb, and Zn in fine fraction (<20μm) from contaminated soils and mine tailings

The present study aims (1) to characterize contaminated soils (n=6) and mine tailings samples (n=3) for As, Cu, Fe, Mn, Ni, Pb, and Zn content; and (2) to assess elemental lung bioaccessibility in fine fraction (d<20μm which might contribute to airborne particulate matter (PM) and thus be inhaled) by means of in vitro tests using Gamble's solution (GS) and an artificial lysosomal fluid (ALF). Elemental concentrations were high in the majority of samples, particularly for As (up to 2040mg·kg^-1), Fe (up to 30.7%), Mn (up to 4360mg·kg^-1), and Zn (up to 4060mg·kg^-1); and elemental concentrations (As, Cu, and Ni) in the sieved fraction (d<20μm) obtained from contaminated soils were significantly higher than in the bulk fraction (<160μm). In vitro tests with ALF yielded much higher bioaccessibility than tests with GS, and the use of ALF in addition to GS is recommended to assess lung bioaccessibility. Bioaccessibility in ALF was high for all elements after 2weeks of testing both in terms of concentration (e.g. up to 1730mg·kg^-1 for As) and percentages (e.g. up to 81% for Pb). The elemental solubilization rate generally declined rapidly and continuously with time. Similarly, bioaccessibility increased rapidly and tended to reach a plateau with time for most samples and metals. However, it is not possible to recommend a general testing duration as the solubilization behavior was highly element and sample-specific.

A smart NIR fluorescent probe for the highly selective detection of palladium

A tailor-made colorimetric and NIR fluorescent probe for Pd⁰ was developed by introducing allyl chloroformate into the methylene blue (MB) fluorophore.

A brief review on recent developments of electrochemical sensors in environmental application for PGMs

This study offers a brief review of the latest developments and applications of electrochemical sensors for the detection of Platinum Group Metals (PGMs) using electrochemical sensors. In particular, significant advances in electrochemical sensors made over the past decade and sensing methodologies associated with the introduction of nanostructures are highlighted. Amongst a variety of detection methods that have been developed for PGMs, nanoparticles offer the unrivaled merits of high sensitivity. Rapid detection of PGMs is a key step to promote improvement of the public health and individual quality of life. Conventional methods to detect PGMs rely on time-consuming and labor intensive procedures such as extraction, isolation, enrichment, counting, etc., prior to measurement. This results in laborious sample preparation and testing over several days. This study reviewed the state-of-the-art application of nanoparticles (NPs) in electrochemical analysis of environmental pollutants. This review is intended to provide environmental scientists and engineers an overview of current rapid detection methods, a close look at the nanoparticles based electrodes and identification of knowledge gaps and future research needs. We summarize electrodes that have been used in the past for detection of PGMs. We describe several examples of applications in environmental electrochemical sensors and performance in terms of sensitivity and selectivity for all the sensors utilized for PGMs detection. NPs have promising potential to increase competitiveness of electrochemical sensors in environmental monitoring, though this review has focused mainly on sensors used in the past decade for PGMs detection. This review therefore provides a synthesis of outstanding performances in recent advances in the nanosensor application for PGMs determination.

Lung bioaccessibility of contaminants in particulate matter of geological origin

Human exposure to particulate matter (PM) has been associated with adverse health effects. While inhalation exposure to airborne PM is a prominent research subject, exposure to PM of geological origin (i.e., generated from soil/soil-like material) has received less attention. This review discusses the contaminants in PM of geological origin and their relevance for human exposure and then evaluates lung bioaccessibility assessment methods and their use. PM of geological origin can contain toxic elements as well as organic contaminants. Observed/predicted PM lung clearance times are long, which may lead to prolonged contact with lung environment. Thus, certain exposure scenarios warrant the use of in vitro bioaccessibility testing to predict lung bioavailability. Limited research is available on lung bioaccessibility test development and test application to PM of geological origin. For in vitro tests, test parameter variation between different studies and concerns about physiological relevance indicate a crucial need for test method standardization and comparison with relevant animal data. Research is recommended on (1) developing robust in vitro lung bioaccessibility methods, (2) assessing bioaccessibility of various contaminants (especially polycyclic aromatic hydrocarbons (PAHs)) in PM of diverse origin (surface soils, mine tailings, etc.), and (3) risk characterization to determine relative importance of exposure to PM of geological origin.

The influence of pH on the in vitro permeation of rhodium through human skin

Workers in precious metals refineries are at risk of exposure to salt compounds of the platinum group metals through inhalation, as well as through the skin. Rhodium salt permeation through the skin has previously been proven using rhodium trichloride (RhCl3) dissolved in synthetic sweat at a pH of 6.5. However, the skin surface pH of refinery workers may be lower than 6.5. The aim of this study was to investigate the influence of pH 6.5 and 4.5 on the in vitro permeation of rhodium through intact Caucasian skin using Franz diffusion cells. A concentration of 0.3 mg mL−1 rhodium was used and analyses were performed using inductively coupled plasma mass spectrometry and inductively coupled plasma optical emission spectrometry. Results indicated a cumulative increase in permeation over 24 h. Rhodium permeation after 12 h was significantly greater at pH 4.5 (1.56 ± 0.24 ng cm−2) than at 6.5 (0.85 ± 0.13 ng cm−2; p = 0.02). At both pH levels, there was a highly significant difference ( p < 0.01) between the mass of rhodium remaining in the skin (1428.68 ± 224.67 ng cm−2 at pH 4.5 and 1029.90 ± 115.96 ng cm−2 at pH 6.5) and the mass that diffused through (0.88 ± 0.17 ng cm−2 at pH 4.5 and 0.62 ± 0.10 ng cm−2 at pH 6.5). From these findings, it is evident that an acidic working environment or low skin surface pH may enhance permeation of rhodium salts, contributing to sensitization and adverse health effects.

A Multimethod Approach for Investigating Algal Toxicity of Platinum Nanoparticles

The ecotoxicity of platinum nanoparticles (PtNPs) widely used in for example automotive catalytic converters, is largely unknown. This study employs various characterization techniques and toxicity end points to investigate PtNP toxicity toward the green microalgae Pseudokirchneriella subcapitata and Chlamydomonas reinhardtii. Growth rate inhibition occurred in standard ISO tests (EC₅₀ values of 15-200 mg Pt/L), but also in a double-vial setup, separating cells from PtNPs, thus demonstrating shading as an important artifact for PtNP toxicity. Negligible membrane damage, but substantial oxidative stress was detected at 0.1-80 mg Pt/L in both algal species using flow cytometry. PtNPs caused growth rate inhibition and oxidative stress in P. subcapitata, beyond what was accounted for by dissolved Pt, indicating NP-specific toxicity of PtNPs. Overall, P. subcapitata was found to be more sensitive toward PtNPs and higher body burdens were measured in this species, possibly due to a favored binding of Pt to the polysaccharide-rich cell wall of this algal species. This study highlights the importance of using multimethod approaches in nanoecotoxicological studies to elucidate toxicity mechanisms, influence of NP-interactions with media/organisms, and ultimately to identify artifacts and appropriate end points for NP-ecotoxicity testing.

Immunotoxicity and Sensitizing Capacity of Metal Compounds Depend on Speciation

Immunotoxicity of metal compounds is an issue of great importance due to the recent industrial application of metals with unknown toxicity on the immune system and the discovery of metal intermediary compounds not sufficiently studied yet. In this report we show results of our study on the immunotoxicity of the following metals: the Platinum group elements (Platinum, Palladium, Rhodium), Titanium and Arsenic. We applied functional and non functional assays and investigated both innate and adaptive immune systems, in particular, cell proliferation, cytokine production by PBMCs and O−2 production by neutrophils. We obtained the following results: only some Ti compounds (Titanocene, Ti ascorbate and Ti oxalate) show immunotoxicity. Trivalent As compounds (Sodium arsenite and tetraphenyl arsonium chloride) are more immunotoxic than the other investigated As compounds. Genotoxicity of Pt group compounds is in the following order: Pt < Rh < Pd. Immunotoxicity of Pt group compounds is in the following order: Pd < Pt < Rh. Lymphocytes and macrophages show a different reaction of neutrophils to metal toxicity. We can conclude that these studies show that metal immunotoxicity depends on speciation. In general speciation provides additional and often essential information in evaluating metal toxicity. However, there are many difficulties in applying speciation in investigating toxico-kinetic aspects to many metals, mainly due to the lack of information about the existence and significance of species and to the lack of analytical methods for measuring species in biological samples.

Batch leaching tests of motherboards to assess environmental contamination by bromine, platinum group elements and other selected heavy metals

In this study, a batch leaching test was executed to evaluate the toxicity associated with chemicals contained in motherboards. The leaching solutions used were distilled water, nitric acid, acetic acid and synthetic acid rain solution. A total of 21 elements including Ag, As, Au, Br, Cd, Co, Cr, Cu, Hf, Ir, Mn, Ni, Os, Pb, Pd, Pt, Rd, Rh, Se, U and Zn were analyzed. In this study, the pH values of all the leachates fell within the range of 2.33-4.88. The highest concentrations of metals were obtained from the acid rain solution, whilst the maximum value of bromine was achieved with solution of acetic acid. Appreciable concentrations of platinum group elements were detected with concentrations around 3.45, 1.43, 1.21 and 22.19 µg L(-1) for Ir, Pd, Pt and Rh, respectively. The different leaching of the motherboards revealed the predominant presence of the toxic substances in the leached from the e-waste.

A colorimetric and fluorescent dual probe for palladium in aqueous medium and live cell imaging

A colorimetric and fluorescent dual probe for palladium species was rationally developed by combining the resorufin fluorophore with allyl chloroformate.

Exposure to Palladium Nanoparticles Affects Serum Levels of Cytokines in Female Wistar Rats

Background

Information currently available on the impact of palladium on the immune system mainly derives from studies assessing the biological effects of palladium salts. However, in the last years, there has been a notable increase in occupational and environmental levels of fine and ultrafine palladium particles released from automobile catalytic converters, which may play a role in palladium sensitization. In this context, the evaluation of the possible effects exerted by palladium nanoparticles (Pd-NPs) on the immune system is essential to comprehensively assess palladium immunotoxic potential.

Aim

Therefore, the aim of this study was to investigate the effects of Pd-NPs on the immune system of female Wistar rats exposed to this xenobiotic for 14 days, by assessing possible quantitative changes in a number of cytokines: IL-1α, IL-2, IL-4, IL-6, IL-10, IL-12, GM-CSF, INF-γ and TNF-α.

Methods

Twenty rats were randomly divided into four exposure groups and one of control. Animals were given a single tail vein injection of vehicle (control group) and different concentrations of Pd-NPs (0.012, 0.12, 1.2 and 12 μg/kg). A multiplex biometric enzyme linked immunosorbent assay was used to evaluate cytokine serum levels.

Results

The mean serum concentrations of all cytokines decreased after the administration of 0.012 μg/kg of Pd-NPs, whereas exceeded the control levels at higher exposure doses. The highest concentration of Pd-NPs (12 μg/kg) induced a significant increase of IL-1α, IL-4, IL-6, IL-10, IL-12, GM-CSF and INF-γ compared to controls.

Discussion and Conclusions

These results demonstrated that Pd-NP exposure can affect the immune response of rats inducing a stimulatory action that becomes significant at the highest administered dose. Our findings did not show an imbalance between cytokines produced by CD4⁺ T helper (Th) cells 1 and 2, thus suggesting a generalized stimulation of the immune system with a simultaneous activation and polarization of the naïve T cells towards Th1 and Th2 phenotype.

The metallobiochemistry of ultratrace levels of platinum group elements in the rat

The use of platinum, palladium and rhodium (Platinum Group Elements - PGEs) and the possibility of exposure to their ultratrace levels is increasing. In fact, the exponential development of metallic PGE-based nanoparticles (<100 nm in size) opens extraordinary perspectives in the areas of electrocatalysts and catalytic converters, magnetic nanopowders, polymer membranes, cancer therapy, coatings, plastics, nanofibres and textiles. Like other metal-based nanoparticles, exposure to PGEs nanoparticles may result in a release of ultratrace amounts of Pt, Pd, Rh ions in the body whose metabolic fate and toxicity still need to be evaluated. Furthermore, PGEs can act as allergic sensitizers by acting as haptens and inducing both type I and IV allergic reactions. In this work we studied the in vivo metabolic patterns of ultratrace levels of potent allergens and sensitizers PGE halogenated salts. (191)Pt, (103)Pd and (101m)Rh radioisotopes were prepared via cyclotron irradiation and used for radiolabelling Na2(191)PtCl4, Na2(103)PdCl4 and Na2(101m)RhCl6 salts. These anionic chlorocomplexes were intraperitoneally injected into rats (114 ng Pt kg(-1) bodyweight; 24 ng Pd kg(-1) b.w.; 16 ng Rh kg(-1) b.w.). At 16 h post-exposure, PGEs were poorly but significantly retained in all tissues analysed. Kidneys, spleen, adrenal gland, liver, pancreas and small intestine were the organs with the highest Pt, Pd, Rh concentrations. In the blood 30-35% of (103)Pd and (191)Pt and 10% of (101m)Rh were recovered in the plasma, mainly bound to albumin and to a less extent to transferrin. The hepatic and renal intracellular distribution showed the highest recovery of (191)Pt, (103)Pd and (101m)Rh in the nuclear fraction (liver) and in the cytosol (kidney). Chromatographic separation and ultrafiltration experiments on kidney and liver cytosols showed the strong ability of biochemical macromolecules to bind (191)Pt, (103)Pd and (101m)Rh, and being responsible for the retention of the three elements in the body. The link to macromolecules is the basis for the sensitizing capacity of PGEs.

Biomonitoring of airborne platinum group elements in urban traffic police officers

In the present study, an attempt was made to study the levels of platinum (Pt), palladium (Pd), and rhodium (Rh) in respirable suspended particulate matter samples and respective blood samples of occupationally exposed traffic personnel in selected sites of Hyderabad city. The maximum concentration of platinum group elements in air dust samples of Hyderabad city were as follows: Pt = 1,416 µg/m(3), Pd = 1,024 µg/m(3), and Rh = 1,352 µg/m(3). The blood samples of occupationally exposed personnel of Hyderabad city showed Pt as high as 6.65, Pd as high as 2.15, and Rh as high as 4.95 µg/l. The results showed an important aspect of bioaccumulation tendency of these metals with increase in age and years of occupational exposure.

Spatial variation of contaminant elements of roadside dust samples from Budapest (Hungary) and Seoul (Republic of Korea), including Pt, Pd and Ir

Roadside dusts were studied to explain the spatial variation and present levels of contaminant elements including Pt, Pd and Ir in urban environment and around Budapest (Hungary) and Seoul (Republic of Korea). The samples were collected from six sites of high traffic volumes in Seoul metropolitan city and from two control sites within the suburbs of Seoul, for comparison. Similarly, road dust samples were obtained two times from traffic focal points in Budapest, from the large bridges across the River Danube, from Margitsziget (an island in the Danube in the northern part of Budapest, used for recreation) as well as from main roads (no highways) outside Budapest. The samples were analysed for contaminant elements by ICP-AES and for Pt, Pd and Ir by ICP-MS. The highest Pt, Pd and Ir levels in road dusts were found from major roads with high traffic volume, but correlations with other contaminant elements were low, however. This reflects automobile catalytic converter to be an important source. To interpret the obtained multi-element results in short, pollution index, contamination index and geo-accumulation index were calculated. Finally, the obtained data were compared with total concentrations encountered in dust samples from Madrid, Oslo, Tokyo and Muscat (Oman). Dust samples from Seoul reached top level concentrations for Cd-Zn-As-Co-Cr-Cu-Mo-Ni-Sn. Just Pb was rather low because unleaded gasoline was introduced as compulsory in 1993. Concentrations in Budapest dust samples were lower than from Seoul, except for Pb and Mg. Compared with Madrid as another continental site, Budapest was higher in Co-V-Zn. Dust from Oslo, which is not so large, contained more Mn-Na-Sr than dust from other towns, but less other metals.

Development and application of an inhalation bioaccessibility method (IBM) for lead in the PM10 size fraction of soil

An approach for assessing the inhalation bioaccessibility of Pb in the PM10 size fraction is presented, using an in vitro simulated epithelial lung fluid to represent the extracellular environment of the lung. The developed inhalation bioaccessibility method (IBM) is applied to a range of urban surface soils and mining wastes obtained from Mitrovica, Kosovo, a site where impacts upon human health following exposure to Pb have been internationally publicised. All Pb determinations were undertaken by inductively coupled plasma mass spectrometry (ICP-MS). The pseudo-total concentration of Pb (microwave acid digestion using aqua-regia) varied between matrices: smelter (20,900-72,800mgkg(-1)), topsoil (274-13,700mgkg(-1)), and tailings (2990mgkg(-1)-25,300mgkg(-1)). The in vitro inhalation bioaccessibility was typically several orders of magnitude lower: smelter (7.0-965mgkg(-1)), topsoil (9.8-1060mgkg(-1)), and tailings (0.7mgkg(-1)-49.2mgkg(-1)). The % inhalation bioaccessibility ranged from 0.02 to 11.0%, with the higher inhalation bioaccessible Pb concentrations being observed for samples from the Bosniak Mahalla area of Mitrovica (an area proposed for the relocation of internally displaced peoples). The estimated inhalation dose (for adults) calculated from the PM10 pseudo-total Pb concentration ranged from 0.369 to 1.284μgkg(-1)BWday(-1) (smelter), 0.005-0.242μgkg(-1)BWday(-1) (topsoil), and 0.053-0.446μgkg(-1)BWday(-1) (tailings). When daily inhalation doses were calculated using the bioaccessible Pb concentration the modelled exposure doses were much lower: smelter (0.0001-0.0170μgkg(-1)BWday(-1)), topsoil (0.0002-0.0187μgkg(-1)BWday(-1)) and tailings (0.0001-0.0009μgkg(-1)BWday(-1)). Modelled for the neutral pH conditions of the interstitial lung environment, the results indicate a low potential inhalation bioaccessibility for Pb in these samples. Given the already elevated environmental Pb burden experienced by the local population, where significant prolonged dust or particulate generating activities are taking place, or where the inhaled particles are phagocytized, then inhalation exposure has the potential to significantly add to the overall Pb burden. Such data are important for local policy makers to better enable them to assess risk, especially in areas where soils/dusts have elevated levels of contamination.

Palladium nanoparticles induce disturbances in cell cycle entry and progression of peripheral blood mononuclear cells: paramount role of ions

There is concern about the possible toxicity of palladium nanoparticles (Pd-NP), as they are released in the environment through many applications. We previously studied the toxicity of Pd-NP at high concentrations; here we address the possible toxicity of Pd-NP at low, subtoxic doses. In particular, we have exposed normal human PBMC entering into the first in vitro mitotic division to Pd-NP and to Pd(IV) ions to evaluate ROS generation and cell cycle progression. We have measured a statistically significant increase of intracellular ROS in Pd(IV) exposed cells, but not in Pd-NP exposed cells. TEM revealed accumulation of lipid droplets and autophagic and mitophagic vacuoles, which appeared more conspicuous in cells exposed to Pd(IV) ions than to Pd-NP. Pd-NP were visible in the cytoplasm of Pd-NP exposed cells. Pd-NP addition was associated with a significant increase of cells within the G0/G1-phase and a significant reduction in GS- and G2/M-phases. Cells exposed to Pd(IV) ions showed a significant amplification of these cell cycle alterations. These results suggest that ions, per se or released by NPs, are the true inducers of Pd toxicity. It will be essential to verify whether the observed disturbance represents a temporary response or might result in permanent alterations.

Fate of platinum metals in the environment

For many years now automotive exhaust catalysts have been used to reduce the significant amounts of harmful chemical substances generated by car engines, such as carbon monoxide, nitrogen oxides, and aromatic hydrocarbons. Although they considerably decrease environmental contamination with the above-mentioned compounds, it is known that catalysts contribute to the environmental load of platinum metals (essential components of catalysts), which are released with exhaust fumes. Contamination with platinum metals stems mainly from automotive exhaust converters, but other major sources also exist. Since platinum group elements (PGEs): platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru) and iridium (Ir) seem to spread in the environment and accumulate in living organisms, they may pose a threat to animals and humans. This paper discusses the modes and forms of PGE emission as well as their impact on the environment and living organisms.