No adverse lung effects of 7- and 28-day inhalation exposure of rats to emissions from petrodiesel fuel containing 20% rapeseed methyl esters (B20) with and without particulate filter – the FuelHealth project

Genotoxicity by rapeseed methyl ester and hydrogenated vegetable oil combustion exhaust products in lung epithelial (A549) cells

Biofuel is an attractive substitute for petrodiesel because of its lower environmental footprint. For instance, the polycyclic aromatic hydrocarbons (PAH) emission per fuel energy content is lower for rapeseed methyl ester (RME) than for petrodiesel. This study assesses genotoxicity by extractable organic matter (EOM) of exhaust particles from the combustion of petrodiesel, RME, and hydrogenated vegetable oil (HVO) in lung epithelial (A549) cells. Genotoxicity was assessed as DNA strand breaks by the alkaline comet assay. EOM from the combustion of petrodiesel and RME generated the same level of DNA strand breaks based on the equal concentration of total PAH (i.e. net increases of 0.13 [95% confidence interval (CI): 0.002, 0.25, and 0.12 [95% CI: 0.01, 0.24] lesions per million base pairs, respectively). In comparison, the positive control (etoposide) generated a much higher level of DNA strand breaks (i.e. 0.84, 95% CI: 0.72, 0.97) lesions per million base pairs. Relatively low concentrations of EOM from RME and HVO combustion particles (<116 ng/ml total PAH) did not cause DNA strand breaks in A549 cells, whereas benzo[a]pyrene and PAH-rich EOM from petrodiesel combusted using low oxygen inlet concentration were genotoxic. The genotoxicity was attributed to high molecular weight PAH isomers with 5-6 rings. In summary, the results show that EOM from the combustion of petrodiesel and RME generate the same level of DNA strand breaks on an equal total PAH basis. However, the genotoxic hazard of engine exhaust from on-road vehicles is lower for RME than petrodiesel because of lower PAH emission per fuel energy content.

Respiratory Health Effects of In Vivo Sub-Chronic Diesel and Biodiesel Exhaust Exposure

Biodiesel, which can be made from a variety of natural oils, is currently promoted as a sustainable, healthier replacement for commercial mineral diesel despite little experimental data supporting this. The aim of our research was to investigate the health impacts of exposure to exhaust generated by the combustion of diesel and two different biodiesels. Male BALB/c mice (n = 24 per group) were exposed for 2 h/day for 8 days to diluted exhaust from a diesel engine running on ultra-low sulfur diesel (ULSD) or Tallow or Canola biodiesel, with room air exposures used as control. A variety of respiratory-related end-point measurements were assessed, including lung function, responsiveness to methacholine, airway inflammation and cytokine response, and airway morphometry. Exposure to Tallow biodiesel exhaust resulted in the most significant health impacts compared to Air controls, including increased airway hyperresponsiveness and airway inflammation. In contrast, exposure to Canola biodiesel exhaust resulted in fewer negative health effects. Exposure to ULSD resulted in health impacts between those of the two biodiesels. The health effects of biodiesel exhaust exposure vary depending on the feedstock used to make the fuel.

Biodiesel feedstock determines exhaust toxicity in 20% biodiesel: 80% mineral diesel blends

To address climate change concerns, and reduce the carbon footprint caused by fossil fuel use, it is likely that blend ratios of renewable biodiesel with commercial mineral diesel fuel will steadily increase, resulting in biodiesel use becoming more widespread. Exhaust toxicity of unblended biodiesels changes depending on feedstock type, however the effect of feedstock on blended fuels is less well known. The aim of this study was to assess the impact of biodiesel feedstock on exhaust toxicity of 20% blended biodiesel fuels (B20). Primary human airway epithelial cells were exposed to exhaust diluted 1/15 with air from an engine running on conventional ultra-low sulfur diesel (ULSD) or 20% blends of soy, canola, waste cooking oil (WCO), tallow, palm or cottonseed biodiesel in diesel. Physico-chemical exhaust properties were compared between fuels and the post-exposure effect of exhaust on cellular viability and media release was assessed 24 h later. Exhaust properties changed significantly between all fuels with cottonseed B20 being the most different to both ULSD and its respective unblended biodiesel. Exposure to palm B20 resulted in significantly decreased cellular viability (96.3 ± 1.7%; p < 0.01) whereas exposure to soy B20 generated the greatest number of changes in mediator release (including IL-6, IL-8 and TNF-α, p < 0.05) when compared to air exposed controls, with palm B20 and tallow B20 closely following. In contrast, canola B20 and WCO B20 were the least toxic with only mediators G-CSF and TNF-α being significantly increased. Therefore, exposure to palm B20, soy B20 and tallow B20 were found to be the most toxic and exposure to canola B20 and WCO B20 the least. The top three most toxic and the bottom three least toxic B20 fuels are consistent with their unblended counterparts, suggesting that feedstock type greatly impacts exhaust toxicity, even when biodiesel only comprises 20% of the fuel.

Dietary Intervention with Blackcurrant Pomace Protects Rats from Testicular Oxidative Stress Induced by Exposition to Biodiesel Exhaust

The exposure to diesel exhaust emissions (DEE) contributes to negative health outcomes and premature mortality. At the same time, the health effects of the exposure to biodiesel exhaust emission are still in scientific debate. The aim of presented study was to investigate in an animal study the effects of exposure to DEE from two types of biodiesel fuels, 1st generation B7 biodiesel containing 7% of fatty acid methyl esters (FAME) or 2nd generation biodiesel (SHB20) containing 7% of FAME and 13% of hydrotreated vegetable oil (HVO), on the oxidative stress in testes and possible protective effects of dietary intervention with blackcurrant pomace (BC). Adult Fisher344/DuCrl rats were exposed by inhalation (6 h/day, 5 days/week for 4 weeks) to 2% of DEE from B7 or SHB20 fuel mixed with air. The animals from B7 (n = 14) and SHB20 (n = 14) groups subjected to filtered by a diesel particulate filter (DPF) or unfiltered DEE were maintained on standard feed. The rats from B7+BC (n = 12) or SHB20+BC (n = 12), exposed to DEE in the same way, were fed with feed supplemented containing 2% (m/m) of BC. The exposure to exhaust emissions from 1st and 2nd generation biodiesel resulted in induction of oxidative stress in the testes. Higher concentration of the oxidative stress markers thiobarbituric acid-reactive substances (TBARS), lipid hydroperoxides (LOOHs), 25-dihydroxycholesterols (25(OH)2Ch), and 7-ketocholesterol (7-KCh) level), as well as decreased level of antioxidant defense systems such as reduced glutathione (GSH), GSH/GSSG ratio, and increased level of oxidized glutathione (GSSG)) were found. Dietary intervention reduced the concentration of TBARS, 7-KCh, LOOHs, and the GSSG level, and elevated the GSH level in testes. In conclusion, DEE-induced oxidative stress in the testes was related to the biodiesel feedstock and the application of DPF. The SHB20 DEE without DPF technology exerted the most pronounced toxic effects. Dietary intervention with BC in rats exposed to DEE reduced oxidative stress in testes and improved antioxidative defense parameters, however the redox balance in the testes was not completely restored.

Toxicity of different biodiesel exhausts in primary human airway epithelial cells grown at air-liquid interface

Biodiesel is created through the transesterification of fats/oils and its usage is increasing worldwide as global warming concerns increase. Biodiesel fuel properties change depending on the feedstock used to create it. The aim of this study was to assess the different toxicological properties of biodiesel exhausts created from different feedstocks using a complex 3D air-liquid interface (ALI) model that mimics the human airway. Primary human airway epithelial cells were grown at ALI until full differentiation was achieved. Cells were then exposed to 1/20 diluted exhaust from an engine running on Diesel (ULSD), pure or 20% blended Canola biodiesel and pure or 20% blended Tallow biodiesel, or Air for control. Exhaust was analysed for various physio-chemical properties and 24-h after exposure, ALI cultures were assessed for permeability, protein release and mediator response. All measured exhaust components were within industry safety standards. ULSD contained the highest concentrations of various combustion gases. We found no differences in terms of particle characteristics for any of the tested exhausts, likely due to the high dilution used. Exposure to Tallow B100 and B20 induced increased permeability in the ALI culture and the greatest increase in mediator response in both the apical and basal compartments. In contrast, Canola B100 and B20 did not impact permeability and induced the smallest mediator response. All exhausts but Canola B20 induced increased protein release, indicating epithelial damage. Despite the concentrations of all exhausts used in this study meeting industry safety regulations, we found significant toxic effects. Tallow biodiesel was found to be the most toxic of the tested fuels and Canola the least, both for blended and pure biodiesel fuels. This suggests that the feedstock biodiesel is made from is crucial for the resulting health effects of exhaust exposure, even when not comprising the majority of fuel composition.

Acute cardiovascular effects of controlled exposure to dilute Petrodiesel and biodiesel exhaust in healthy volunteers: a crossover study

BACKGROUND

Air pollution derived from combustion is associated with considerable cardiorespiratory morbidity and mortality in addition to environmental effects. Replacing petrodiesel with biodiesel may have ecological benefits, but impacts on human health remain unquantified. The objective was to compare acute cardiovascular effects of blended and pure biodiesel exhaust exposure against known adverse effects of petrodiesel exhaust (PDE) exposure in human subjects. In two randomized controlled double-blind crossover studies, healthy volunteers were exposed to PDE or biodiesel exhaust for one hour. In study one, 16 subjects were exposed, on separate occasions, to PDE and 30% rapeseed methyl ester biodiesel blend (RME30) exhaust, aiming at PM10 300 μg/m3. In study two, 19 male subjects were separately exposed to PDE and exhaust from a 100% RME fuel (RME100) using similar engine load and exhaust dilution. Generated exhaust was analyzed for physicochemical composition and oxidative potential. Following exposure, vascular endothelial function was assessed using forearm venous occlusion plethysmography and ex vivo thrombus formation was assessed using a Badimon chamber model of acute arterial injury. Biomarkers of inflammation, platelet activation and fibrinolysis were measured in the blood.

RESULTS

In study 1, PDE and RME30 exposures were at comparable PM levels (314 ± 27 μg/m3; (PM10 ± SD) and 309 ± 30 μg/m3 respectively), whereas in study 2, the PDE exposure concentrations remained similar (310 ± 34 μg/m3), but RME100 levels were lower in PM (165 ± 16 μg/m3) and PAHs, but higher in particle number concentration. Compared to PDE, PM from RME had less oxidative potential. Forearm infusion of the vasodilators acetylcholine, bradykinin, sodium nitroprusside and verapamil resulted in dose-dependent increases in blood flow after all exposures. Vasodilatation and ex vivo thrombus formation were similar following exposure to exhaust from petrodiesel and the two biodiesel formulations (RME30 and RME100). There were no significant differences in blood biomarkers or exhaled nitric oxide levels between exposures.

CONCLUSIONS

Despite differences in PM composition and particle reactivity, controlled exposure to biodiesel exhaust was associated with similar cardiovascular effects to PDE. We suggest that the potential adverse health effects of biodiesel fuel emissions should be taken into account when evaluating future fuel policies.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01337882 /NCT01883466. Date of first enrollment March 11, 2011, registered April 19, 2011, i.e. retrospectively registered.

Comparative study on gene expression profile in rat lung after repeated exposure to diesel and biodiesel exhausts upstream and downstream of a particle filter

Biodiesel is considered as a valuable and less toxic alternative to diesel. However, cellular and molecular effects of repeated exposure to biodiesel emissions from a recent engine equipped with a diesel particle filter (DPF) remain to be characterized. To gain insights about this point, the lung transcriptional signatures were analyzed for rats (n = 6 per group) exposed to filtered air, 30% rapeseed biodiesel (B30) blend or reference diesel (RF0), upstream and downstream a DPF, for 3 weeks (3 h/day, 5 days/week). Genomic analysis revealed a modest regulation of gene expression level (lower than a 2-fold) by both fuels and a higher number of genes regulated downstream the DPF than upstream, in response to either RF0 or to B30 exhaust emissions. The presence of DPF was found to notably impact the lung gene signature of rats exposed to B30. The number of genes regulated in common by both fuels was low, which is likely due to differences in concentrations of regulated pollutants in exhausts, notably for compound organic volatiles, polycyclic aromatic hydrocarbons, NO or NOx. Nevertheless, we have identified some pathways that were activated for both exhaust emissions, such as integrin-, IGF-1- and Rac-signaling pathways, likely reflecting the effects of gas phase products. By contrast, some canonical pathways relative to "oxidative phosphorylation" and "mitochondrial dysfunction" appear as specific to B30 exhaust emission; the repression of transcripts of mitochondrial respiratory chain in lung of rats exposed to B30 downstream of DPF supports the perturbation of mitochondria function. This study done with a recent diesel engine (compliant with the European IV emission standard) and commercially-available fuels reveals that the diesel blend composition and the presence of an after treatment system may modify lung gene signature of rats repeatedly exposed to exhaust emissions, however in a rather modest manner.

Inflammation, oxidative stress and genotoxicity responses to biodiesel emissions in cultured mammalian cells and animals

Biodiesel fuels are alternatives to petrodiesel, especially in the transport sector where they have lower carbon footprint. Notwithstanding the environmental benefit, biodiesel fuels may have other toxicological properties than petrodiesel. Particulate matter (PM) from petrodiesel causes cancer in the lung as a consequence of delivery of genotoxic polycyclic aromatic hydrocarbons, oxidative stress and inflammation. We have reviewed articles from 2002 to 2019 (50% of the articles since 2015) that have described toxicological effects in terms of genotoxicity, oxidative stress and inflammation of biodiesel exhaust exposure in humans, animals and cell cultures. The studies have assessed first generation biodiesel from different feedstock (e.g. rapeseed and soy), certain second generation fuels (e.g. waste oil), and hydrogenated vegetable oil. It is not possible to rank the potency of toxicological effects of specific biodiesel fuels. However, exposure to biodiesel exhaust causes oxidative stress, inflammation and genotoxicity in cell cultures. Three studies in animals have not indicated genotoxicity in lung tissue. The database on oxidative stress and inflammation in animal studies is larger (13 studies); ten studies have reported increased levels of oxidative stress biomarkers or inflammation, although the effects have been modest in most studies. The cell culture and animal studies have not consistently shown a different potency in effect between biodiesel and petrodiesel exhausts. Both increased and decreased potency have been reported, which might be due to differences in feedstock or combustion conditions. In conclusion, combustion products from biodiesel and petrodiesel fuel may evoke similar toxicological effects on genotoxicity, oxidative stress and inflammation.

Biodiesel fuels: A greener diesel? A review from a health perspective

Biodiesels have been promoted as a greener alternative to diesel with decreased emissions and health effects. To investigate the scientific basis of the suggested environmental and health benefits offered by biodiesel, this review examines the current state of knowledge and key uncertainties of pollutant profiles of biodiesel engine exhaust and the associated the respiratory and cardiovascular outcomes. The ease and low cost of biodiesel production has facilitated greater distribution and commercial use. The pollutant profile of biodiesel engine exhaust is distinct from diesel, characterised by increased NOx and aldehyde emissions but decreased CO and CO₂. Lower engine-out particulate matter mass concentrations have also been observed over a range of feedstocks. However, these reduced emissions have been attributable to a shift towards smaller sized particulate emissions. The toxicity of biodiesel engine exhaust has been investigated in vitro using various lung cell, in vivo evaluating responses induced in animals and through several human exposure studies. Discrepancies exist across results reported by in vitro and in vivo studies, which may be attributable to differences in biodiesel feedstocks, engine characteristics, operating conditions or use of aftertreatment systems across test scenarios. The limited human testing further suggests short-term exposure to biodiesel engine exhaust is associated with cardiopulmonary outcomes that are comparable to diesel. Additional information about the health effects of biodiesel engine exhaust exposure is required for effective public health policy.

Toxicity of Exhaust Fumes (CO, NOx) of the Compression-Ignition (Diesel) Engine with the Use of Simulation

Nowadays more and more emphasis is placed on the protection of the natural environment. Scientists notice that global warming is associated with an increase of carbon dioxide emissions, which results inter alia from the combustion of gasoline, oil, and coal. To reduce the problem of pollution from transport, the EU is introducing increasingly stringent emission standards which should correspond to sustainable conditions of the environment during the operation of motor vehicles. The emissivity value of substances, such as nitrogen oxides (NOx), hydrocarbons (HC), carbon monoxide (CO), as well as solid particles, was determined. The aim of this paper was to examine, by means of simulation in the Scilab program, the exhaust emissions generated by the 1.3 MultiJet Fiat Panda diesel engine, and in particular, carbon monoxide and nitrogen oxides (verified on the basis of laboratory tests). The Fiat Panda passenger car was selected for the test. The fuels supplied to the tested engine were diesel and FAME (fatty acid methyl esters). The Scilab program, which simulated the diesel engine operation, was the tool for analyzing the exhaust toxicity test. The combustion of biodiesel does not necessarily mean a smaller amount of exhaust emissions, as could be concluded on the basis of information contained in the subject literature. The obtained results were compared with the currently valid EURO-6 standard, for which the limit value for CO is 0.5 g/km, and for NOx − 0.08 g/km, and it can be seen that the emission of carbon monoxide did not exceed the standards in any case examined. Unfortunately, when analyzing the total emissions of nitrogen oxides, the situation was completely the opposite and the emissions were exceeded by 20–30%.

Lung effects of 7- and 28-day inhalation exposure of rats to emissions from 1st and 2nd generation biodiesel fuels with and without particle filter - The FuelHealth project

Increased use of 1st and 2nd generation biofuels raises concerns about health effects of new emissions. We analyzed cellular and molecular lung effects in Fisher 344 rats exposed to diesel engine exhaust emissions (DEE) from a Euro 5-classified diesel engine running on B7: petrodiesel fuel containing 7% fatty acid methyl esters (FAME), or SHB20 (synthetic hydrocarbon biofuel): petrodiesel fuel containing 7% FAME and 13% hydrogenated vegetable oil. The Fisher 344 rats were exposed for 7 consecutive days (6 h/day) or 28 days (6 h/day, 5 days/week), both with and without diesel particle filter (DPF) treatment of the exhaust in whole body exposure chambers (n = 7/treatment). Histological analysis and analysis of cytokines and immune cell numbers in bronchoalveolar lavage fluid (BALF) did not reveal adverse pulmonary effects after exposure to DEE from B7 or SHB20 fuel. Significantly different gene expression levels for B7 compared to SHB20 indicate disturbed redox signaling (Cat, Hmox1), beta-adrenergic signaling (Adrb2) and xenobiotic metabolism (Cyp1a1). Exhaust filtration induced higher expression of redox genes (Cat, Gpx2) and the chemokine gene Cxcl7 compared to non-filtered exhaust. Exposure time (7 versus 28 days) also resulted in different patterns of lung gene expression. No genotoxic effects in the lungs were observed. Overall, exposure to B7 or SHB20 emissions suggests only minor effects in the lungs.

The potential of omics approaches to elucidate mechanisms of biodiesel-induced pulmonary toxicity

BACKGROUND

Combustion of biodiesels in place of fossil diesel (FD) has been proposed as a method of reducing transport-related toxic emissions in Europe. While biodiesel exhaust (BDE) contains fewer hydrocarbons, total particulates and carbon monoxide than FD exhaust (FDE), its high nitrogen oxide and ultrafine particle content may still promote pulmonary pathophysiologies.

MAIN BODY

Using a complement of in vitro and in vivo studies, this review documents progress in our understanding of pulmonary responses to BDE exposure. Focusing initially on hypothesis-driven, targeted analyses, the merits and limitations of comparing BDE-induced responses to those caused by FDE exposure are discussed within the contexts of policy making and exploration of toxicity mechanisms. The introduction and progression of omics-led workflows are also discussed, summarising the novel insights into mechanisms of BDE-induced toxicity that they have uncovered. Finally, options for the expansion of BDE-related omics screens are explored, focusing on the mechanistic relevance of metabolomic profiling and offering rationale for expansion beyond classical models of pulmonary exposure.

CONCLUSION

Together, these discussions suggest that molecular profiling methods have identified mechanistically informative, novel and fuel-specific signatures of pulmonary responses to biodiesel exhaust exposure that would have been difficult to detect using traditional, hypothesis driven approaches alone.

The effects of 1st and 2nd generation biodiesel exhaust exposure on hematological and biochemical blood indices of Fisher344 male rats - The FuelHealth project

Diesel exhaust emissions (DEE), being one of the main causes of ambient air pollution, exert a detrimental effect on human health and increase morbidity and mortality related to cardiovascular and pulmonary diseases. Therefore, the objective of the present study was to investigate potential adverse effects of exhausts emissions from B7 fuel, the first-generation biofuel containing 7% of fatty acid methyl esters (FAME), and SHB20 fuel, the second-generation biofuel containing 20% FAME/hydrotreated vegetable oil (HVO), after a whole-body exposure with and without diesel particle filter (DPF). The experiment was performed on 95 male Fischer 344 rats, divided into 10 groups (8 experimental, 2 control). Animals were exposed to DEE (diluted with charcoal-filtered room air to 2.1-2.2% (v/v)) for 7 or 28 days (6 h/day, 5 days/week) in an inhalation chamber. DEE originated from Euro 5 engine with or without DPF treatment, run on B7 or SHB20 fuel. Animals in the control groups were exposed to clean air. Our results showed that the majority of haematological and biochemical parameters examined in blood were at a similar level in the exposed and control animals. However, exposure to DEE from the SHB20 fuel caused an increase in the number of red blood cells (RBC) and haemoglobin concentration. Moreover, 7 days exposure to DEE from SHB20 fuel induced genotoxic effects manifested by increased levels of DNA single-strand breaks in peripheral blood lymphocytes. Furthermore, inhalation of both types of DEE induced oxidative stress and caused imbalance of anti-oxidant defence enzymes. In conclusion, exposure to DEE from B7, which was associated with higher exposure to polycyclic aromatic hydrocarbons, resulted in decreased number of T and NK lymphocytes, while DEE from SHB20 induced a higher level of DNA single-strand breaks, oxidative stress and increased red blood cells parameters. Additionally, DPF technology generated increased number of smaller PM and made the DEE more reactive and more harmful, manifested as deregulation of redox balance.

Comparative study of diesel and biodiesel exhausts on lung oxidative stress and genotoxicity in rats

The contribution of diesel exhaust to atmospheric pollution is a major concern for public health, especially in terms of occurrence of lung cancers. The present study aimed at addressing the toxic effects of a repeated exposure to these emissions in an animal study performed under strictly controlled conditions. Rats were repeatedly exposed to the exhaust of diesel engine. Parameters such as the presence of a particle filter or the use of gasoil containing rapeseed methyl ester were investigated. Various biological parameters were monitored in the lungs to assess the toxic and genotoxic effects of the exposure. First, a transcriptomic analysis showed that some pathways related to DNA repair and cell cycle were affected to a limited extent by diesel but even less by biodiesel. In agreement with occurrence of a limited genotoxic stress in the lungs of diesel-exposed animals, small induction of γ-H2AX and acrolein adducts was observed but not of bulky adducts and 8-oxodGuo. Unexpected results were obtained in the study of the effect of the particle filter. Indeed, exhausts collected downstream of the particle filter led to a slightly higher induction of a series of genes than those collected upstream. This result was in agreement with the formation of acrolein adducts and γH2AX. On the contrary, induction of oxidative stress remained very limited since only SOD was found to be induced and only when rats were exposed to biodiesel exhaust collected upstream of the particle filter. Parameters related to telomeres were identical in all groups. In summary, our results point to a limited accumulation of damage in lungs following repeated exposure to diesel exhausts when modern engines and relevant fuels are used. Yet, a few significant effects are still observed, mostly after the particle filter, suggesting a remaining toxicity associated with the gaseous or nano-particular phases.