Impact of biomass burning on the concentration of polycyclic aromatic compounds and in vitro toxicity of atmospheric particulate matter from Ribeirão Preto-SP

Author(s)

Caroline Scaramboni

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (PCARP/BC)
• Defense date: 2023-11-27

Examining board members

Maria Lucia Arruda de Moura Campos; Célia dos Anjos Alves; Maria de Fatima Andrade; Elza Tiemi Sakamoto Hojo

• Advisor: Maria Lucia Arruda de Moura Campos; Daniel Junqueira Dorta

Abstract

Particulate Matter (PM) in the atmosphere poses a risk to human health as it was associated with respiratory, cardiovascular, and cancer-related diseases. Among the organic compounds present in PM, polycyclic aromatic hydrocarbons (PAHs) and their oxygenated and nitrogenated derivatives have received special attention due to their high mutagenic and carcinogenic potential. In this study, PM was collected in the city of Ribeirão Preto, São Paulo, Brazil, which is located in a sugarcane-producing region that is still affected by biomass burning, despite the discontinuation of sugarcane leaves burning before manual harvesting. Given the high frequency of fires and the dense population in the region, the impact of biomass burning on the emission of PAHs and derivatives and the in vitro toxicity of PM needs to be further investigated. For this purpose, size-fractionated PM samples were collected in the dry and wet seasons of the years 2020 and 2021. Anhydrosugars levoglucosan, mannosan, and galactosan were used as markers of biomass burning. Simultaneous determination of PAHs, oxy-PAHs, nitro-PAHs, and anhydrosugars was performed using gas chromatography-mass spectrometry after organic extraction of PM with acetonitrile via sonication. The extraction method was previously optimized and satisfactorily validated, resulting in a relatively simple method that uses small amounts of organic solvent when compared to various methods in the literature, allowing for the analysis of samples collected with a low-volume sampler. The median concentration of the total 15 PAHs determined was 2.3 ± 1.8 ng m-3 (n = 19), of which 63% were present in PM < 1.0 µm (PM1.0). Oxy-PAH and nitro-PAH concentrations were about an order of magnitude lower. PM < 2.5 µm (PM2.5) collected in the dry season, when most fires occur, had three times higher total concentrations of PAHs and oxy-PAHs than in the wet season and had positive correlations with the number of fire spots and anhydrosugars concentrations. These results, together with the fact that biomass burning explained 65% of the data variance (principal component analysis - PCA), highlighted the importance of this practice as a source of PAHs and oxy-PAHs in the region\'s atmosphere. On the other hand, the results indicated that nitro-PAHs were primarily emitted by diesel-powered vehicles. The equivalent concentration of benzo[a]pyrene was four times higher in the dry season than in the wet season and increased by about 23 times during a local fire. The cytotoxicity and genotoxicity of organic extracts of PM1.0 were evaluated through in vitro tests with human liver HepG2 cells. For both types of tests, significant toxicity was observed only for samples collected during the dry season. Persistent DNA damage was also observed, which may have impaired the DNA repair system. In addition to working with the PM extract, this study investigated the cytotoxic and genotoxic effects of the PAH retene using HepG2 cells. Retene had minimal effects on cell viability but induced DNA strand breaks, micronucleus formation, and the formation of reactive oxygen species (ROS) in a concentration and time-dependent manner. Retene activated checkpoint kinase 1 (Chk1) phosphorylation, an indicator of replication stress and chromosomal instability, corroborating the increased formation of micronuclei. An antioxidant, N-acetylcysteine (NAC), was observed to have a protective effect on ROS generation and DNA damage signaling, suggesting oxidative stress as a key mechanism of the observed genotoxic effects of retene in HepG2 cells. In conclusion, the results of this study contribute to a better understanding of the environmental and health challenges posed by biomass burning and the urgency of addressing this issue in the context of current global climate change. (AU)

• FAPESP's process: 18/17931-0 - Atmospheric particulate matter from a region impacted by biomass burning: sources and toxicity
• Grantee: Caroline Scaramboni
• Support Opportunities: Scholarships in Brazil - Doctorate