Elsevier

Toxicology in Vitro

Volume 57, June 2019, Pages 67-75
Toxicology in Vitro

Primary human bronchial epithelial cell responses to diesel and biodiesel emissions at an air-liquid interface

https://doi.org/10.1016/j.tiv.2019.02.005Get rights and content

Highlights

  • Increasing biodiesel percentage is diesel fuel decreases particle mass and particle number in engine emissions.

  • Increasing triacetin percentage in biodiesel fuel increases particle number while decreasing particle mass in emissions.

  • The addition of biodiesel and/or triacetin to diesel may be more detrimental to pHBECs than conventional diesel emissions

Abstract

Introduction

Diesel emissions have a high level of particulate matter which can cause inflammation and oxidative stress in the airways. A strategy to reduce diesel particulate matter and the associated adverse effects is the use of biodiesels and fuel additives. However, very little is known about the biological effects of these alternative emissions. The aim of this study is to compare the effect of biodiesel and triacetin/biodiesel emissions on primary human bronchial epithelial cells (pHBECs) compared to diesel emissions.

Methods

pHBECs were exposed to diesel, biodiesel (20%, 50% and 100% biodiesel derived from coconut oil) and triacetin/biodiesel (4% and 10% triacetin) emissions for 30 min at air-liquid interface. Cell viability (cellular metabolism, cell death, CASP3 mRNA expression and BCL2 mRNA expression), inflammation (IL-8 and IL-6 secretion), antioxidant production (HO-1 mRNA expression) and xenobiotic metabolism (CYP1a1 mRNA expression) were measured.

Results

Biodiesel emissions (B50) reduced cell viability, and increased oxidative stress. Triacetin/biodiesel emissions (B90) decreased cell viability and increased antioxidant production, inflammation and xenobiotic metabolism. Biodiesel emissions (B100) reduced cell viability, and increased IL-8 secretion and xenobiotic metabolism.

Conclusions

Biodiesel substitution in diesel fuel and triacetin substitution in biodiesel can increase the adverse effects of diesel emissions of pHBECs. Further studies of the effect of these diesel fuel alternatives on pHBECs are required.

Introduction

Diesel emission are a major contributor to outdoor air pollution. Acute exposure to diesel emissions causes inflammation and oxidative stress in the airways (Salvi et al., 1999). Chronic, long term exposure to diesel emissions diesel emission exposure has been associated with increased COPD risk and mortality (Hart et al., 2006). These adverse effects have been associated with the high level of particulate matter in diesel emissions (Ristovski et al., 2012; Steiner et al., 2016; Ma et al., 2017). A common strategy to reduce the level of particulate matter from diesel emissions is the substitution of diesel fuel with a biodiesel (Lin et al., 2011). Coconut-biodiesel, a common biodiesel in Asia, is cost effective, has close properties to diesel and is globally available (Kalam et al., 2003; Jayed et al., 2009). Combustion of coconut oil biodiesel has been shown to decrease CO, hydrocarbon content, PAH and decrease total PM from diesel emissions (Kalam et al., 2003; Bünger et al., 2016).

Another strategy to reduce diesel particulate matter is to use a fuel additive. Triacetin is a common fuel additive. It is made from the acetylation of glycerol, which is a by-product of biodiesel transesterification (Casas et al., 2010). Therefore, this addictive is a cost-effective feedstock to add to biodiesel fuels. Triacetin increases the oxygen content of fuel (Zare et al., 2016), which improves the combustion efficiency of biodiesel and reduces emissions (Rahman et al., 2014).

Biodiesel and fuel additives are emerging interventions to address global increases in fuel consumption, global warming and the adverse effects of fossil fuels (Kulkarni and Dalai, 2006). Research has shown that coconut-biodiesel can reduce genotoxicity and mutagenicity of diesel emissions (Yang et al., 2017). However, very little is known about the potential health effects of coconut-biodiesel and triacetin as a fuel additive to biodiesel. The aim of this study was to compare the effect of biodiesel and triacetin/biodiesel blends on pHBECs to conventional diesel emissions at an air-liquid interface.

Section snippets

Cell culture

Primary HBECs were isolated and cultured from surgical resection tissue donated, with written informed consent, by patients with lung adenocarcinoma. This study was approved by the Human Research Ethics Committees of The Prince Charles Hospital and The University of Queensland. Briefly, a bronchial ring was isolated from the lung resection specimen and incubated in a dissociation mix containing Pronase (Roche, Penzberg, Germany), Minimal Essentials Media-alpha (MEMα, Invitrogen, USA),

Characterisation of fuel and emissions

When studying the effects in diesel emission exposure under physiological conditions, it is important for the diesel emission dose (particle mass as mg/m3) to be accurate to a real-life scenario. For example, the city of Beijing, China is known for its high particulate matter air pollution. Over a 9-year study, it was shown that ambient PM2.5 in Beijing can range from 0.001–1.2 mg/m3 (Liu et al., 2015). Higher doses outside this range may be considered irrelevant to the in vivo situation. In

Main results

The results of this study indicate that coconut-biodiesel and triacetin/biodiesel fuel blends may be more detrimental to pHBECs than conventional diesel emissions. This was demonstrated through four main findings. Firstly, D100, B50 and B90 fuel blends produced emissions containing nucleation mode particles from a diesel engine with a DOC and DPF after treatment device. Secondly, coconut-biodiesel emissions can decrease cell viability and increase oxidative stress when compared to conventional

Conclusions

Although biodiesel fuels and fuel additives can reduce the pollutant load in diesel emissions, very little is understood about the potential health impacts of these alternate fuels. This study has shown that biodiesel and triacetin/biodiesel can increase the adverse effects of diesel emissions of pHBECs. This has provided insight into the effect of these diesel fuel alternative on pHBECs, and supports future research into the biological responses to different fuel additives and biodiesels.

Funding

This research was funded by the Australian Research Council Discovery grant (DP120100126), The Prince Charles Hospital Foundation PhD Scholarship (PhD2014–10) and National Health and Medical Research Council Career Development Fellowship (APP1026215).

Research ethics

This study was approved by the Human Research Ethics Committee for the Metro North Hospital and Health Service and the University of Queensland (HREC/11/QPCH/196: Interventions to reduce pulmonary toxicity of ultrafine particles: SSA/11/QPCH/233).

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