Respirable stone particles differ in their ability to induce cytotoxicity and pro-inflammatory responses in cell models of the human airways

Background Respirable stone- and mineral particles may be a major constituent in occupational and ambient air pollution and represent a possible health hazard. However, with exception of quartz and asbestos, little is known about the toxic properties of mineral particles. In the present study, the pro-inflammatory and cytotoxic responses to six stone particle samples of different composition and with diameter below 10 μm were assessed in human bronchial epithelial cells (HBEC3-KT), THP-1 macrophages and a HBEC3-KT/THP-1 co-culture. Moreover, particle-induced lysis of human erythrocytes was assessed to determine the ability of the particles to lyse biological membranes. Finally, the role of the NLRP3 inflammasome was assessed using a NLRP3-specific inhibitor and detection of ASC oligomers and cleaved caspase-1 and IL-1β. A reference sample of pure α-quartz was included for comparison. Results Several stone particle samples induced a concentration-dependent increase in cytotoxicity and secretion of the pro-inflammatory cytokines CXCL8, IL-1α, IL-1β and TNFα. In HBEC3-KT, quartzite and anorthosite were the most cytotoxic stone particle samples and induced the highest levels of cytokines. Quartzite and anorthosite were also the most cytotoxic samples in THP-1 macrophages, while anorthosite and hornfels induced the highest cytokine responses. In comparison, few significant differences between particle samples were detected in the co-culture. Adjusting responses for differences in surface area concentrations did not fully account for the differences between particle samples. Moreover, the stone particles had low hemolytic potential, indicating that the effects were not driven by membrane lysis. Pre-incubation with a NLRP3-specific inhibitor reduced stone particle-induced cytokine responses in THP-1 macrophages, but not in HBEC3-KT cells, suggesting that the effects are mediated through different mechanisms in epithelial cells and macrophages. Particle exposure also induced an increase in ASC oligomers and cleaved caspase-1 and IL-1β in THP-1 macrophages, confirming the involvement of the NLRP3 inflammasome. Conclusions The present study indicates that stone particles induce cytotoxicity and pro-inflammatory responses in human bronchial epithelial cells and macrophages, acting through NLRP3-independent and -dependent mechanisms, respectively. Moreover, some particle samples induced cytotoxicity and cytokine release to a similar or greater extent than α-quartz. Thus, these minerals warrant further attention in future research.publishedVersio

Pavement wear and airborne dust pollution in Norway

In several large cities in Norway the traffic volume is high. The use of studded tires and other friction enhancing measures during winter leads to significant pavement wear, which in turn leads to an increase in the amount of airborne particulate matter, often exceeding the limits set in the ambient air regulation. This represents a nuisance or health risk for people being exposed to the pollution. According to regulations set by the European Union particulate matter is measured and regulated through mass concentration of particles less than 10 μm in diameter (PM10). However, studies of health effects related to exposure to particulate matter have shown that particle properties like morphology and composition are essential regarding toxicity and in considering risk of developing disease. There seems to be a more complex relationship between dust pollution and health effects, which cannot be explained with just the mass concentration alone. This makes it necessary to characterize the physical and chemical properties of the road dust. Characterization of road dust particles is important to provide basis for a better understanding of the pavement wear and production of road dust and its influence on human health in urban areas. The overall purpose of this study has been to characterize particles generated from pavement wear qualitatively and quantitatively. Five papers are included in the thesis. Paper I and II present field investigations of road dust sampled in the vertical direction close to an urban road in Trondheim, Norway. In Paper III different laboratory methods have been used for simulation of pavement wear and road dust generation by studded tires. Paper IV and V describe how aggregate size, driving speeds and vehicle tires affect pavement wear and particle properties. The main conclusions from the study are: Studded tires used in the winter season in Norway are the main cause for generation of road dust from pavement wear. If studded tires were not used, there would be much less suspended particulate matter originating from wear of pavements in urban air. Studded tires produce much more dust particles from wear of pavements compared to nonstudded tires. For instance, at 60 km/h studded tires produce 30-40 times more TSP compared to non-studded tires on an SMA 8 pavement measured in an indoor test facility. The airborne road dust is composed of almost 90 % by weight of mineral particles under winter conditions, and approximately 50 % of the particles have size smaller than 25 μm (D50). Based on all samples analyzed, D10 is 3 μm and D90 is 60 μm. However, agglomeration of particles seems to make the measured particle size distribution coarser than it really is. Studded tires generate dust with finer particle size distribution than non-studded tires. The main fraction of the particles can be described as rounded particles, with average roundness value around 0.6. The specific surface area of the sample is dependent on the amount of organic material present in the sample and the particle size distribution. In general, field samples have higher specific surface area than dust particles generated in laboratory because of higher organic content. However, finely ground particles produced in laboratory may exhibit even higher surface area than field samples of road dust because of finer particle size distribution. Surface area is an important factor in health considerations since the reactivity of particles increase with increasing surface area. Other factors affecting the generation of particles from pavement wear are the driving speed and type of rock material used in the pavement. Test results show that the PM10 concentration measured under laboratory conditions is reduced by 32-49 % when reducing the driving speed from 70 to 50 km/h, 52-83 % when reducing the driving speed from 50 to 30 km/h, and 76-89 % when reducing the driving speed from 70 to 30 km/h. The driving speed affects the particle size and the particle shape distributions. Increasing driving speed generate particles with finer particle size distribution and more irregular particles. The rock material used in the pavement affect the amount of dust generated, the composition, the particle size distribution, the shape distribution, and the specific surface area. Some mineral types are regarded harmful to health, for example quartz and asbestos which are classified as carcinogenic. The total amount of airborne dust (TSP) and PM10 can be very different; a high TSP does not necessarily lead to a high PM10 concentration and vice versa. This study has shown that it is possible to produce dust comparable to studded tire wear by use of simple laboratory techniques. This has significance with regard to cost because it is not necessary to build expensive test sections when the purpose is to generate and characterize the dust from pavement wear. The small scale asphalt testing procedures, Prall and Tröger, are the methods best suited to give fine material which is comparable to particles generated from the Pavement testing machine (PTM). It also seems that one can test the aggregate alone to get reasonably good samples for analysis of dust from wear by studded tires. Among the aggregate testing procedures, the Los Angeles (LA) method gives the best correlation with the PTM. The dust produced by Tröger and Prall is more similar to the dust produced in the field because the dust is generated from asphalt mixtures, while the dust produced by LA, Nordic ball mill (KM) and micro-Deval (MD) comes from the aggregate only. However, none of these methods include/simulate the effect of the car tire, only the studs. The results have shown that apart from the use of studded tires, the rock material used in the pavement has a significant influence on the airborne dust generated. It is therefore important to carefully select the rock materials for use in urban road pavements. The aggregate type affects both the amount of dust generated and the particle properties. Existing knowledge shows that the finer the particles, the greater will be their potential effects on health. Since driving speed influences both the amounts of road dust generated and the particle size distribution, one may have to consider the use of speed restrictions in urban areas in winter time to reduce the potentially hazardous effects of road dust. However, this has to be balanced against other traffic conditions such as congestion

Miljøvennlige vegdekker : sluttrapport for arbeidspakke 3: støv

Statens vegvesens etatsprosjekt Miljøvennlige vegdekker (2004-2008). Prosjektet har hatt følgende effektmål: - Færre støyplagede langs norske veger og gater. - Bedre luftkvalitet i tettbygde strøk. Prosjektet har vært organisert i 9 arbeidspakker. Denne rapporten oppsummerer arbeidet som er utført i arbeidspakke 3: Støv. Følgende konklusjoner kan trekkes etter gjennomført prosjektperiode: - Støvproduksjon skyldes hovedsakelig bruk av piggdekk. - Utenom asfaltsdekkes egenskaper påvirkes produksjon av svevestøv fra et asfaltdekke av trafikkhastighet og piggdekkandel. - For tette asfaltdekker, med hulrom < 6 %, påvirkes produksjonen av svevestøv av steinkvalitet uttrykt gjennom Møllerverdi. En bør derfor, hvor en ønsker å redusere støvproduksjon, vurdere strengere krav til steinkvalitet enn hva som er beskrevet i håndbok 018. - For tette asfaltdekker, med hulrom 2 mm. Det er viktig at mengden er så høy som mulig for å redusere støvproduksjon. En konsekvens av dette er at dekketyper med øvre steinstørrelse < 8 mm ikke bør anvendes på veger med høy piggdekkandel. - For porøse dekker, med hulrom > 6 %, ser en at det er flere faktorer som påvirker produksjonen av svevestøv. I tillegg til steinkvalitet og materiale > 2 mm påvirkes åpne dekker av hulrom, bindemiddeltype (PMB) og bindemiddelinnhold. - Salt brukt til vintervedlikehold påvirker i første rekke bestandighet til porøse dekker. Tette dekke påvirkes lite. - Salt medfører våt vegbane over større tidsperiode. Våt vegbane gir økt slitasje

Miljøvennlige vegdekker : statusrapport på støv for Norge, Sverige og Finland

Arbeidspakke Støv i Miljøvennlige vegdekker fikk i 2006 laget en litteraturoversikt/status innen vegstøvproblematikken for landene Norge, Sverige og Finland. Denne rapporten er delt inn i tre deler; del 1 omhandler Norge, del 2 Sverige og del 3 Finland

Role of different mechanisms in pro-inflammatory responses triggered by traffic-derived particulate matter in human bronchiolar epithelial cells

Abstract Background Traffic-derived particles are important contributors to the adverse health effects of ambient particulate matter (PM). In Nordic countries, mineral particles from road pavement and diesel exhaust particles (DEP) are important constituents of traffic-derived PM. In the present study we compared the pro-inflammatory responses of mineral particles and DEP to PM from two road tunnels, and examined the mechanisms involved. Methods The pro-inflammatory potential of 100 µg/mL coarse (PM10-2.5), fine (PM2.5-0.18) and ultrafine PM (PM0.18) sampled in two road tunnels paved with different stone materials was assessed in human bronchial epithelial cells (HBEC3-KT), and compared to DEP and particles derived from the respective stone materials. Release of pro-inflammatory cytokines (CXCL8, IL-1α, IL-1β) was measured by ELISA, while the expression of genes related to inflammation (COX2, CXCL8, IL-1α, IL-1β, TNF-α), redox responses (HO-1) and metabolism (CYP1A1, CYP1B1, PAI-2) was determined by qPCR. The roles of the aryl hydrocarbon receptor (AhR) and reactive oxygen species (ROS) were examined by treatment with the AhR-inhibitor CH223191 and the anti-oxidant N-acetyl cysteine (NAC). Results Road tunnel PM caused time-dependent increases in expression of CXCL8, COX2, IL-1α, IL-1β, TNF-α, COX2, PAI-2, CYP1A1, CYP1B1 and HO-1, with fine PM as more potent than coarse PM at early time-points. The stone particle samples and DEP induced lower cytokine release than all size-fractionated PM samples for one tunnel, and versus fine PM for the other tunnel. CH223191 partially reduced release and expression of IL-1α and CXCL8, and expression of COX2, for fine and coarse PM, depending on tunnel, response and time-point. Whereas expression of CYP1A1 was markedly reduced by CH223191, HO-1 expression was not affected. NAC reduced the release and expression of IL-1α and CXCL8, and COX2 expression, but augmented expression of CYP1A1 and HO-1. Conclusions The results indicate that the pro-inflammatory responses of road tunnel PM in HBEC3-KT cells are not attributed to the mineral particles or DEP alone. The pro-inflammatory responses seem to involve AhR-dependent mechanisms, suggesting a role for organic constituents. ROS-mediated mechanisms were also involved, probably through AhR-independent pathways. DEP may be a contributor to the AhR-dependent responses, although other sources may be of importance

The importance of mineralogical composition for the cytotoxic and pro-inflammatory effects of mineral dust

Background Respirable mineral particles represent a potential health hazard in occupational settings and ambient air. Previous studies show that mineral particles may induce cytotoxicity and inflammatory reactions in vitro and in vivo and that the potency varies between samples of different composition. However, the reason for these differences is largely unknown and the impact of mineralogical composition on the biological effects of mineral dust remains to be determined. Methods We have assessed the cytotoxic and pro-inflammatory effects of ten mineral particle samples of different composition in human bronchial epithelial cells (HBEC3-KT) and THP-1-derived macrophages, as well as their membranolytic properties in erythrocytes. Moreover, the results were compiled with the results of recently published experiments on the effects of stone particle exposure and analysed using linear regression models to elucidate which mineral components contribute most to the toxicity of mineral dust. Results While all mineral particle samples were more cytotoxic to HBEC3-KT cells than THP-1 macrophages, biotite and quartz were among the most cytotoxic in both cell models. In HBEC3-KT cells, biotite and quartz also appeared to be the most potent inducers of pro-inflammatory cytokines, while the quartz, Ca-feldspar, Na-feldspar and biotite samples were the most potent in THP-1 macrophages. All particle samples except quartz induced low levels of membranolysis. The regression analyses revealed associations between particle bioactivity and the content of quartz, muscovite, plagioclase, biotite, anorthite, albite, microcline, calcite, chlorite, orthopyroxene, actinolite and epidote, depending on the cell model and endpoint. However, muscovite was the only mineral consistently associated with increased cytotoxicity and cytokine release in both cell models. Conclusions The present study provides further evidence that mineral particles may induce cytotoxicity and inflammation in cells of the human airways and that particle samples of different mineralogical composition differ in potency. The results show that quartz, while being among the most potent samples, does not fully predict the toxicity of mineral dust, highlighting the importance of other particle constituents. Moreover, the results indicate that the phyllosilicates muscovite and biotite may be more potent than other minerals assessed in the study, suggesting that this group of sheet-like minerals may warrant further attention

Characterization of tire and road wear microplastic particle contamination in a road tunnel: From surface to release

Road pollution is one of the major sources of microplastic particles to the environment. The distribution of tire, polymer-modified bitumen (PMB) and tire and road wear particles (TRWP) in different tunnel compartments were explored: road surface, gully-pots and tunnel wash water. A new method for calculating TRWP using Monte Carlo simulation is presented. The highest concentrations on the surface were in the side bank (tire:13.4 ± 5.67;PMB:9.39 ± 3.96; TRWP:22.9 ± 8.19 mg/m2), comparable to previous studies, and at the tunnel outlet (tire:7.72 ± 11.2; PMB:5.40 ± 7.84; TRWP:11.2 ± 16.2 mg/m2). The concentrations in gully-pots were highest at the inlet (tire:24.7 ± 26.9; PMB:17.3 ± 48.8; TRWP:35.8 ± 38.9 mg/g) and comparable to values previously reported for sedimentation basins. Untreated wash water was comparable to road runoff (tire:38.3 ± 10.5; PMB:26.8 ± 7.33; TRWP:55.3 ± 15.2 mg/L). Sedimentation treatment retained 63% of tire and road wear particles, indicating a need to increase the removal efficiency to prevent these from entering the environment. A strong linear relationship (R2-adj=0.88, p < 0.0001) between total suspended solids (TSS) and tire and road wear rubber was established, suggesting a potential for using TSS as a proxy for estimating rubber loads for monitoring purposes. Future research should focus on a common approach to analysis and calculation of tire, PMB and TRWP and address the uncertainties related to these calculations

Characterization of tire and road wear microplastic particle contamination in a road tunnel: From surface to release

Road pollution is one of the major sources of microplastic particles to the environment. The distribution of tire, polymer-modified bitumen (PMB) and tire and road wear particles (TRWP) in different tunnel compartments were explored: road surface, gully-pots and tunnel wash water. A new method for calculating TRWP using Monte Carlo simulation is presented. The highest concentrations on the surface were in the side bank (tire:13.4 ± 5.67;PMB:9.39 ± 3.96; TRWP:22.9 ± 8.19 mg/m2), comparable to previous studies, and at the tunnel outlet (tire:7.72 ± 11.2; PMB:5.40 ± 7.84; TRWP:11.2 ± 16.2 mg/m2). The concentrations in gully-pots were highest at the inlet (tire:24.7 ± 26.9; PMB:17.3 ± 48.8; TRWP:35.8 ± 38.9 mg/g) and comparable to values previously reported for sedimentation basins. Untreated wash water was comparable to road runoff (tire:38.3 ± 10.5; PMB:26.8 ± 7.33; TRWP:55.3 ± 15.2 mg/L). Sedimentation treatment retained 63% of tire and road wear particles, indicating a need to increase the removal efficiency to prevent these from entering the environment. A strong linear relationship (R2-adj=0.88, p < 0.0001) between total suspended solids (TSS) and tire and road wear rubber was established, suggesting a potential for using TSS as a proxy for estimating rubber loads for monitoring purposes. Future research should focus on a common approach to analysis and calculation of tire, PMB and TRWP and address the uncertainties related to these calculations