Subway Particles Are More Genotoxic than Street Particles and Induce Oxidative Stress in Cultured Human Lung Cells

Abstract

Epidemiological studies have shown an association between airborne particles and a wide range of adverse health effects. The mechanisms behind these effects include oxidative stress and inflammation. Even though traffic gives rise to high levels of particles in the urban air, people are exposed to even higher levels in the subway. However, there is a lack of knowledge regarding how particles from different urban subenvironments differ in toxicity. The main aim of the present study was to compare the ability of particles from a subway station and a nearby very busy urban street, respectively, to damage DNA and to induce oxidative stress. Cultured human lung cells (A549) were exposed to particles, DNA damage was analyzed using single cell gel electrophoresis (the comet assay), and the ability to induce oxidative stress was measured as 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) formation in lung cell DNA. We found that the subway particles were approximately eight times more genotoxic and four times more likely to cause oxidative stress in the lung cells. When the particles, water extracts from the particles, or particles treated with the metal chelator deferoxamine mesylate were incubated with 2'-deoxyguanosine (dG) and 8-oxodG was analyzed, we found that the oxidative capacity of the subway particles was due to redox active solid metals. Furthermore, analysis of the atomic composition showed that the subway particles to a dominating degree (atomic %) consisted of iron, mainly in the form of magnetite (Fe3O4). By using electron microscopy, the interaction between the particles and the lung cells was shown. The in vitro reactivity of the subway particles in combination with the high particle levels in subway systems give cause of concern due to the high number of people that are exposed to subway particles on a daily basis. To what extent the subway particles cause health effects in humans needs to be further evaluated.

Granulometric and magnetic properties of deposited particles in the Beijing subway and the implications for air quality management

“…Pulmonary inflammation and cardiovascular disease risk increased after air pollution control during the Olympic period (Huang et al, 2012a;Huang et al, 2012b). Moreover, enrichment of heavy metals, like Fe and others, in fine particles could also induce potential health consequences (Bachoual et al, 2007;Bigert et al, 2008;Karlsson et al, 2008;Karlsson et al, 2005;Morman and Plumlee, 2014). Considering the presence of PM sustained and accelerated by the strong air convection in the Beijing subway environment, there is immense scope for the collaboration between environmental and toxicological specialists.…”

“…The secondary source is the particles carried by regular passengers and air flow from the outside urban environment (Kang et al, 2008;Li et al, 2006). Earlier toxicological research has pointed out that subway PMs induce oxidative stress in cultured human lung cell (Karlsson et al, 2005(Karlsson et al, , 2008 and impose strong self-limiting biological reactions on rodents (Bachoual et al, 2007), suggesting that the same PM might trigger health hazards in passengers. While lung cancer incidence was not increased , workers in the subway service were observed to suffer a long-term inflammatory process .…”

“…Previous attempts to assess the environmental conditions in the subway system have focused on the concentration and chemical composition of PM, with contradictory results (Aarnio et al, 2005;Boudia et al, 2006;Chillrud et al, 2004;Guo et al, 2014;Karlsson et al, 2005;Lu et al, 2015;Salma et al, 2007;Gómez-Perales et al, 2007;Querol et al, 2012) attributed to the different designs of the subway systems (Nieuwenhuijsen et al, 2007).…”

Particle Emissions From Rail Traffic: A Literature Review

“…The genotoxicity and oxidative stress effects of particles in the Stockholm subway have been compared with similar effects of aboveground particles by Karlsson et al (2005). They reported that the subway particles were eight times more genotoxic and four times more effective at causing oxidative stress than were aboveground particles.…”

Installation of platform screen doors and their impact on indoor air quality: Seoul subway trains

“…Particularly, the composition of PM emitted from tunnels includes mainly iron compounds such as magnetite (Fe 3 O 4 ), hematite (Fe 2 O 3 ), and Fe metal (Jung et al, 2012;Mugica-Álvarez et al, 2012;Salma et al, 2007). With regard to the toxicity of those specific compounds, Karlsson et al (2005) reported that the subway particles were approximately eight times more genotoxic and four times more likely to cause oxidative stress in lung cells.…”