Assessment of the human health risks and toxicity associated to particles (pm10, pm2.5 and pm1), organic pollutants and metals around cement plants
- Autores: Francisco Sánchez Soberón
- Directores de la Tesis: Marta Schuhmacher Ansuategui (dir. tes.), Joaquim Rovira Solano (codir. tes.)
- Lectura: En la Universitat Rovira i Virgili ( España ) en 2018
- Idioma: español
- Tribunal Calificador de la Tesis: José Luis Domingo Roig (presid.), Xavier Querol Carceller (secret.), Cristina María Branquinho Fernandes (voc.)
- Programa de doctorado: Programa de Doctorado en Nanociencia, Materiales e Ingeniería Química por la Universidad Rovira i Virgili
- Materias:
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- Resumen
Particulate Matter (PM) is considered the most hazardous air pollutant. Its effects are mainly focused on the respiratory and cardiovascular system, and range from increasing coughing and asthma, to lung cancer and heart attacks. These effects depend profoundly on the physicochemical properties of the PM. The smaller the size, and the higher the content in toxicants (i.e.: heavy metals, polycyclic aromatic hydrocarbons (PAHs), quinones, and endotoxins) the more hazardous the PM is. Since its composition is highly variable depending on sources and meteorological conditions, for regulatory purposes PM is usually classified into two categories attending to its size: PM10 and PM2.5 (smaller than 10 and 2.5 µm respectively). Besides these two fractions, it is lately becoming usual to focus also on those particles smaller than 1 µm (PM1), since their small size allow them to get to deeper parts of the respiratory system.
Particulate matter is released as a consequence of several natural and anthropogenic activities, such as volcanoes, sea spray, traffic, and industries. One of the industrial activities historically recognized as a source of PM is the cement manufacture. In this industry, great amounts of raw materials and fuels are combusted together till reaching temperatures close to 1500ºC needed to form the clinker. In order to save energy and minimize production costs, different kinds of wastes and byproducts from other industries are used inside the cement kiln as both, alternative fuels and raw materials. The combination of this wide array of materials, joined with the high temperature processes undergoing inside the cement kiln introduces a high variability in the physicochemical characteristics of PM released from the stack of cement industries. Furthermore, storage, transport, and processing of raw materials and clinker could generate fugitive emissions of PM.
Despite the great body of knowledge already published focused on the hazardous potential of cement PM, most of it is focused on the study of chemical composition of PM10. Furthermore, some aspects of these particles (such as their toxicity) have not been properly addressed.To surpass this gap we decided to study the physicochemical characteristics and toxicity of PM10, PM2.5, and PM1 nearby a cement plant located in the outskirts of Barcelona (Spain) in different seasons. To know the environmental threats that population was facing, we calculated the exposure and human health risks derived from the inhalation of this pollutant. Finally, we elucidated the contribution from the cement plant to overall environmental PM levels.
To do so, we first sampled PM using high and low volume samplers in a school nearby the cement plant. High volume samplers were loaded with quartz filters (QF), while low volume were loaded with polycarbonate filters (PCF). These filters were weighted before and after sampling under same temperature and humidity conditions to know the PM mass, and, consequently, the PM environmental concentrations.
Subsequently, QF were subjected to the following analitical techniques to elucidate its chemical composition: • Most metals were determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), except Ca, Fe, K, Mg, Na and P that were determined by Inductively Coupled Plasma Optical Emission Spectrometry techniques (ICP-OES).
• Organic compounds (PAHs, hopanes, saccharides and derivates, biomass combustion products, and dicarboxylic acids) were determined by Gas Chromatography coupled to Mass Spectrometry (GC-MS).
• Soluble ions (Cl-, SO42-, NO3-, and NH4+) were determined by Ionic Chromatography.
• Carbonaceous materials (total, organic, and elemental carbon) were determined by Pyrolysis.
On the other hand PCF were reserved for to microscopy and toxicity following the next procedures: • To obtain microscopic images, a small portion of the filter was subjected to Field Emission Scanning Electron Microscopy (FESEM).
• The remaining filter was used to extract PM powder, which was then exposed to cells to study toxicity.
Exposure was calculated by using an integrated infiltration and dosimetry model. Using as inputs the levels of PM and time-activity pattern of three population groups (children, adults, and retired), we calculated the exposure in different environments (home, work, and outdoors) and the deposition of the three PM fractions in the different parts of the respiratory tract. Using the exposure, and the concentrations of toxic metals and PAHs, human health risks assessment were calculated. Lastly, using the chemical characterization it was possible to calculate the contribution of cement plants to total environmental PM.
Our results showed that around 60% of the PM10 mass collected nearby the cement plant is comprised of PM1 regardless of season. Winter registered the highest levels of PM and organic compounds, due to the increase in number and intensity of PM sources and meteorological conditions. Fine fractions (PM2.5 and PM1) showed a greater composition in most toxicants, such as some heavy metals (As, Pb, Cd, Mn, Cr (VI)) and PAHs. Microscopy showed a great influence of combustion processes (i.e. traffic, domestic heating and cement plant) in PM2.5, while a higher influence of mineral and biological sources was patent in bigger particles.
Regarding toxicity, oxidative potential, mortality, and mucus secretion of tracheobronchial cells were higher after exposure to PM2.5 than PM10. On the other hand, cells exposed to PM10 suffered a higher disruption of their cell barrier integrity. Histological observation of the tissues exposed to PM2.5 showed a higher mucus release and greater size and density of vacuoles than tissues exposed to PM10.
Despite the low share of time spent in the open, outdoor activities accounted for most of the deposited mass of PM in the respiratory tract. While PM10 was mostly retained in the nasal area, PM2.5 and PM1 were able to get to lungs. Similar amounts of PM2.5 and PM1 reached the lung regardless of population group, which is especially concerning for children. Non-carcinogenic risks were below the safety threshold (Hazard Quotient<1) for every measured toxicant (i.e. toxic metals and PAHs). Carcinogenic risks were below the threshold considered as acceptable (1 case of cancer every 100,000 inhabitants) for most metals and PAHs, except for Cr (VI), that reached a value of around 3 cases of cancer out of 100,000 inhabitants.
Finally, after applying complimentary tools of source apportionment it was seen that combustion sources were the majoritarian contributors to overall PM pool. By studying inorganic components it was possible to deduce that cement plant was the most prevalent source during winter. Subsequent application of Multivariate Curve Resolution by Alternating Least Squares (MCR-ALS) onto organic components of PM was used to confirm that, as seen in the chemical characterization and microscopy, contribution from combustion sources were higher when decreasing the PM size. Studying isotopic ratio of samples confirmed this trend.
The general conclusion of this thesis is that physicochemical characteristics of coarse (PM10-2.5), fine (PM2.5) and quasi-ultrafine particles (PM1) in areas influenced by cement plants are different, and depend profoundly on PM size and seasonality. Consequently, toxicity and human health risks derived from these particles are variable, and are determined by the PM fraction and the contribution from cement plant and other sources.
