Short-term oral toxicity of three biodiesels and an ultra-low sulfur diesel in male rats

Transformer mineral oil ingestion induces systemic sub-acute toxicity in Wistar rats

We investigated the potential toxicities associated with the sub-acute ingestion of transformer mineral oil (TMO) at a heated low dose (HLD-50 mg/kg), heated high dose (HHD-500 mg/kg) and unheated high dose (UHD-500 mg/kg) in Wistar rats. There were increases in red blood cells and haemoglobin levels in HHD females and UHD males respectively versus control. The serum total proteins, albumin, and creatinine of the HHD females showed a significant increase versus control. The HHD males and UHD groups showed significant increase in liver malondialdehyde versus control. The livers of HHD groups had bile duct proliferation while those of HLD females and UHD groups showed focal areas of periportal chronic inflammation. HHD groups had kidneys with mild chronic inflammation and the HHD and UHD groups showed small intestines with chronic inflammation. In conclusion, sub-acute oral administration of TMO induced various degrees of dermal, haematological, hepatic, renal and small-intestinal toxicities in rats.

Co-administration of a Rhododendron tomentosum extract does not affect mercury tissue concentrations and excretion rate in methylmercury-treated adult male rats

Objectives

Consumption of fish/seafood is clearly linked to higher mercury levels in human tissue samples. However, correlations between methylmercury (MeHg) intakes calculated from dietary surveys and mercury body burdens are usually weak and can vary across populations. Different factors may affect MeHg absorption, distribution, metabolism and excretion, including co-exposures to phytochemicals and antibiotics, which were shown to affect mercury body burdens in rodents. Based on the observation that rat pups developmentally exposed to MeHg and a Rhododendron tomentosum extract (Labrador Tea) presented significantly higher blood mercury levels at weaning compared to pups exposed to MeHg alone, the modulation of MeHg toxicokinetics by Labrador Tea was further investigated in adult rats.

Results

Total mercury levels were quantified in the blood, liver, kidney and feces of adult male rats exposed to MeHg (1.2 mg/kg bodyweight/day, for 3 weeks) administered either alone or in combination with Labrador Tea (100 mg/kg bodyweight/day) or with an antibiotics cocktail (to inhibit MeHg demethylation by gut bacteria). While the reduced fecal excretion and higher blood mercury levels expected from antibiotics-treated rats were observed, mercury levels in samples from Labrador Tea-treated rats were not significantly different from those measured in samples from rats exposed to MeHg alone.

Electronic supplementary material

The online version of this article (10.1186/s13104-019-4409-7) contains supplementary material, which is available to authorized users.

Assessment of three plant-based biodiesels using a Daphnia magna bioassay

Biodiesel is an alternative fuel that is gradually replacing petroleum-based diesel use. Although biodiesel is considered friendlier to the environment, the potential toxic effects of biodiesel to aquatic organisms are still uncertain due to the wide range of feedstocks used to generate the fuel. The aquatic cladoceran Daphnia magna (D. magna) has been commonly used as a lethal and/or sub-lethal toxicological model organism in ecological risk assessments for contaminated water environments. In this work, we evaluated whether significant differences exist in the sensitivity of freshwater aquatic life to different biodiesels. The acute toxicity of three plant-based biodiesels was investigated using D. magna over a 96-h period. In addition, diesel fuel was tested as a reference. Increased immobility was observed as time progressed following exposure. Testing revealed of the four fuel products, diesel proved most toxic to D. magna, with half maximal effective concentration (EC₅₀) values of 4.7 μg/mL (24 h) and 3.4 μg/mL (72 h). Among the biodiesels, safflower methyl biodiesel was most toxic, with EC₅₀ values of 1026 μg/mL (24 h) and 71 μg/mL (48 h). Our data indicate that although not all biodiesels were toxic, the short-term exposure of D. magna to sub-lethal concentrations of biodiesels affects their mobility and thus decreases their reproductive potential. Overall, this research provides insights into the sub-lethal effects of biodiesels on an aquatic organism.

The Effects of Biodiesel and Crude Oil on the Foraging Behavior of Rusty Crayfish, Orconectes rusticus

Environmental pollutants, such as crude oil and other petroleum-based fuels, inhibit and limit an organism's ability to perceive a chemical stimulus. Despite the increased use of alternative fuels, such as biodiesel, there have been few studies investigating the impact of these chemicals on the behavior of aquatic organisms. The purpose of this study was to compare the sublethal effects of biodiesel and crude oil exposure on chemically mediated behaviors in a freshwater keystone species. Crayfish (Orconectes rusticus) were tested on their ability to respond appropriately to a positive chemical stimulus within a Y-maze choice paradigm. Behavior was quantified by measuring time spent finding an odor source, duration of time spent at the odor source, percentage of crayfish that found the odor source, and percentage of crayfish that chose the correct arm of the arena. Results indicated negative impacts of both biodiesel and crude oil on the ability of crayfish to locate the food source. However, there were no significant differences between behavioral performances when crayfish were exposed to crude oil compared with biodiesel. Thus, biodiesel and crude oil have equally negative effects on the chemosensory behavior of crayfish. These findings indicate that biodiesel has the potential to have similar negative ecological impacts as other fuel source toxins.

Biochemical responses, morphometric changes, genotoxic effects and CYP1A expression in the armored catfish Pterygoplichthys anisitsi after 15 days of exposure to mineral diesel and biodiesel

Despite being considered friendlier to the environment, biodiesel fuel can be harmful to aquatic organisms, especially when combined with petroleum diesel fuel. In this work we evaluated the effects of mineral diesel fuel containing increasing concentrations of biodiesel (5% and 20%, namely B5 and B20) and pure biodiesel (B100), at concentrations of 0.001 and 0.01mLL(-1), after 15 days of exposure, in armored catfish (Pterygoplichtys anisitsi). Toxicity tests were also performed to estimate LC50 values (96h) for each compound. Biotransformation enzymes [ethoxyresorufin-O-deethylase (EROD), and glutathione S-transferase (GST)] as well as oxidative stress markers (superoxide dismutase, SOD, catalase, CAT, glutathione peroxidase, GPx, and the level of lipid peroxidation) were measured in liver and gills after treatment. Genotoxic effects were also accessed in erythrocytes using the comet assay and by evaluating the frequency of micronuclei formation. Further, the mRNA of cytochrome P450 1A (CYP1A) was also measured in liver. Mortality was not observed even exposure to concentrations as high as 6.0mLL(-1). EROD and GST activities were increased after B5 and B20 treatments; however, CYP1A mRNA induction was not observed. SOD and CAT activities were decreased, but GPx was significantly higher for all treatments in gills. There were no significant changes in lipid peroxidation, but genotoxicity markers revealed that all treatments increased comet scores. Fuels B5 and B20 increased micronuclei frequency. Our results indicate that despite being less toxic, biodiesel may cause sublethal alterations in fish that may alter long term health.

Development of a sensitive in vitro assay to quantify the biological activity of pro-inflammatory phorbol esters in Jatropha oil

New health safety concerns may arise from the increasing production and use of Jatropha oil, a biodiesel feedstock that also contains toxic, pro-inflammatory, and co-carcinogenic phorbol esters. Based on the exceptional sensitivity of Madin-Darby canine kidney (MDCK) cells to the model phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), a robust bioassay was developed to quantify the biological activity of Jatropha phorbol esters directly in oil, without sample extraction. We first verified that the characteristic response of MDCK cells to TPA was also observed following direct exposure to phorbol esters in Jatropha oil. We further confirmed that similarly to TPA, Jatropha oil's phorbol esters can activate protein kinase C (PKC). We then assessed the transcriptional response of MDCK cells to Jatropha oil exposure by measuring the expression of cyclooxygenase-2 (COX-2), a gene involved in inflammatory processes which is strongly upregulated following PKC activation. Based on the parameterization of a TPA dose-response curve, the transcriptional response of MDCK cells to Jatropha oil exposure was expressed in term of TPA toxic equivalent (TEQ), a convenient metric to report the inflammatory potential of complex mixtures. The sensitive bioassay described in this manuscript may prove useful for risk assessment, as it provides a quantitative method and a convenient metric to report the inflammatory potential of phorbol esters in Jatropha oil. This bioassay may also be adapted for the detection of bioactive phorbol esters in other matrices.

Biochemical responses in armored catfish (Pterygoplichthys anisitsi) after short-term exposure to diesel oil, pure biodiesel and biodiesel blends

Biodiesel fuel is gradually replacing petroleum-based diesel oil use. Despite the biodiesel being considered friendlier to the environment, little is known about its effects in aquatic organisms. In this work we evaluated whether biodiesel exposure can affect oxidative stress parameters and biotransformation enzymes in armored catfish (Pterygoplichthys anisitsi, Loricariidae), a South American endemic species. Thus, fish were exposed for 2 and 7d to 0.01mLL(-1) and 0.1mLL(-1) of pure diesel, pure biodiesel (B100) and blends of diesel with 5% (B5) and 20% (B20) biodiesel. Lipid peroxidation (malondialdehyde) levels and the activities of the enzymes glutathione S-transferase, superoxide dismutase, catalase and glutathione peroxidase were measured in liver and gills. Also, DNA damage (8-oxo-7, 8-dihydro-2'-deoxyguanosine) levels in gills and 7-ethoxyresorufin-O-deethylase activity in liver were assessed. Pure diesel, B5 and B20 blends changed most of the enzymes tested and in some cases, B5 and B20 induced a higher enzyme activity than pure diesel. Antioxidant system activation in P. anisitsi was effective to counteract reactive oxygen species effects, since DNA damage and lipid peroxidation levels were maintained at basal levels after all treatments. However, fish gills exposed to B20 and B100 presented increased lipid peroxidation. Despite biodiesel being more biodegradable fuel that emits less greenhouse gases, the increased lipid peroxidation showed that biofuel and its blends also represent hazards to aquatic biota.

Effects of Jatropha oil on rats following 28-day oral treatment

Jatropha oil is an emerging feedstock for the production of biodiesels. The increasing use of this nonedible, toxic oil will result in higher potential for accidental exposures. A repeated-dose 28-day oral toxicity study was conducted to provide data for risk assessment. Jatropha oil diluted in corn oil was administered by gavage to male and female rats at 0.5, 5, 50 and 500 mg kg(-1) body weight per day for 28 consecutive days. Control rats were administered corn oil only. The growth rates and consumption of food and water were monitored. At necropsy, organs were weighed and hematological parameters assessed. Serum clinical chemistry and C-reactive protein were measured and histological examinations of organs and tissues were performed. Markedly depressed growth rate was observed in males and females receiving Jatropha oil at 500 mg kg(-1) per day. Decreased white blood cell and lymphocyte counts were detected in females at 50 and 500 mg kg(-1) per day and in males at 500 mg kg(-1) per day. These changes were correlated to mild and reversible histological changes in male and female spleens. In the liver, a mild increase in portal hepatocytes cytoplasm density was observed in males and females, while periportal vacuolation was observed exclusively in females. Mild acinar proliferation was observed in the female mammary glands at all dose levels. It is concluded that Jatropha oil produces adverse effects on female rats starting at 50 mg kg(-1) per day with decreased white blood cell and lymphocyte counts and at 500 mg kg(-1) per day in both genders in term of depressed growth rates.

Trace and major element levels in rats after oral administration of diesel and biodiesel derived from opium poppy (Papaver somniferum L.) seeds

The study investigated the toxic effects of diesel and biodiesel derived from opium poppy ( Papaver somniferum L.) oil seeds on the trace and major elements in kidney, lung, liver, and serum of rats. By the end of 21 days, trace and major element concentrations in kidney, lung, and liver tissues and the serum were measured using inductively coupled plasma–optical emission spectroscopy. We observed that trace and major element levels in kidney, lung, and liver tissues and the serum changed. Especially, important differences were detected in trace and major element concentrations in kidney and lung tissues. In kidney tissue, the concentration differences of calcium, sodium, and zinc (Zn) were found between diesel and biodiesel groups. In lung tissue, the concentration differences of cadmium, lithium, magnesium, manganese, and Zn were found between diesel and biodiesel groups. Among the significant findings, Zn concentration in serum and liver tissue of diesel and biodiesel were different from control ( p < 0.05). However, the metal levels of biodiesel group were similar to control group. Due to lesser toxicity of biodiesel, it could be considered as an alternate fuel.

Evaluation of oxidant-antioxidant status in oral toxicity of fish oil methyl esters and diesel fuel in male rats

This study was conducted to compare the effects of oral toxicity induced by fish oil biodiesel and diesel fuel. Diesel and fish oil biodiesel were administered by oral gavage to rats. For this purpose, 35 rats were divided into five groups. Sunflower oil of 250 mg kg(-1) was administered to the rats in the control group by oral gavage. The rats in the D250 and D500 groups were administered by oral gavage 250 mg kg(-1) and 500 mg kg(-1) of diesel fuel dissolved in equal amounts of sunflower oil, respectively. The rats in the F250 and F500 groups were administered by oral gavage 250 mg kg(-1) and 500 mg kg(-1) of fish oil biodiesel dissolved in equal amounts of sunflower oil, respectively. At the end of the study, malondialdehyde (MDA) and reduced glutathione (GSH) levels were measured in the whole blood; catalase (CAT) activity level was measured in erythrocytes; and nitrite (NO2) and nitrate (NO3) levels were measured in the serum. It was observed that the whole blood MDA levels of the diesel groups were considerably different from those in the control and fish oil biodiesel groups (p < 0.001). GSH levels in the control group were observed to be considerably different from those in all other groups (p < 0.001). Serum NO3 concentrations in the diesel groups were found to be considerably different from those in the control and biodiesel groups. Serum NO2 concentrations in one of the diesel groups were significantly different from those in the control and biodiesel groups (p < 0.01 and p < 0.05, respectively). The CAT activity of the control group was observed to be different from that in the other groups. According to these results, both fish oil biodiesel and diesel fuel are thought to cause lipid peroxidation. It was observed that fish oil biodiesel does not induce as much oxidative damage as does the diesel fuel. It is suggested that fish oil biodiesel should be preferred as an alternative to the diesel.

Bioelement status with oral administration of fish oil methyl ester and diesel fuel in male rats

This paper is a study on the effects on the amounts of trace elements in case of possible repeat accidental or environmental exposure with fish oil biodiesel. For this purpose, 35 male Wistar albino rats were used in the study. Rats were divided into five groups. The first group was determined as the control group. The rats in this group were gavaged orally with 250 mg/kg sunflower oil. The rats in the second and third groups were administered by oral gavage of 250 mg/kg (D1) and 500 mg/kg (D2) diesel fuel mixed with equal amounts of sunflower oil, respectively. The rats in the fourth group were administered by oral gavage of 250 mg/kg fish oil biodiesel (F1) and the rats in the fifth group were administered by oral gavage of 500 mg/kg fish oil biodiesel (F2), both mixed with equal amounts of sunflower oil. At the end of the study, bioelement concentrations in the serum and the kidney, lung, and liver tissues were measured using inductively coupled plasma-optical emission spectroscopy. It was observed that serum Ca, Mg, and Sr concentrations were significantly (p<0.001) higher and Cu concentration was significantly (p<0.01) higher in the control group than in the biodiesel groups. Kidney Mg concentration was significantly (p<0.01) lower in the control group than in the diesel groups. Kidney Mg concentration was significantly (p<0.001) lower in the D2 group than in the F2 group. Kidney Mg concentration was significantly (p<0.01) lower in the control group than in the diesel groups. Lung Cd, Co, Cu, Cr, Na, and Zn concentrations were different significantly higher in the control group than in the other groups. Liver Al concentration was different significantly higher in the control group than in the other groups. Liver Ca concentration was significantly (p<0.05) higher in the control group than in the biodiesel groups. Serum and lung tissue bioelements concentrations were lower in diesel and biodiesel groups than in control group. Due to consumption for biochemical reaction of these elements, bioelements concentration could be low in diesel and biodiesel groups. Some trace elements concentrations in the kidney and liver were very high in the diesel groups. High concentration of these elements in the diesel groups might cause toxic effects. Fish oil biodiesel could be chosen as an alternative fuel instead of diesel fuel.

Diesel and biodiesels induce hepatic palmitoyl-CoA oxidase enzymatic activity through different molecular mechanisms in rats

Induction of palmitoyl-CoA oxidase enzymatic activity in rat liver suggests that ingestion of diesel and biodiesels can cause mild hepatic peroxisomal proliferation. Surprisingly, quantification by immunochemistry of the enzyme itself (ACOX1) revealed that palmitoyl-CoA oxidase enzymatic activity correlates with ACOX1 protein level following exposure to diesel, but not following exposure to biodiesels. Quantification of CYP4A1, another biomarker of peroxisomal proliferation, further indicates that contrary to diesel, the effects of biodiesels appear to be independent of this pathway. There are two ACOX1 protein isoforms that exhibit different enzymatic activities depending on the substrate. The results of our enzymatic assays performed on substrates presenting different carbon chain lengths (octanoyl-CoA and palmitoyl-CoA) are compatible with the hypothesis of a differential regulation of the ACOX1 isoforms by diesel and biodiesels. Further studies will be required to precisely determine the molecular mechanisms by which diesel and biodiesels induce palmitoyl-CoA oxidase activity in rat liver.

Effects of 5-chloro-2-methyl-4-isothiazolin-3-one and other candidate biodiesel biocides on rat alveolar macrophages and NR8383 cells

Biocides are added to biodiesels to inhibit and remove microbial growth. The effects of 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT), a candidate biodiesel biocide, were studied using freshly isolated rat alveolar macrophages (AM) and NR8383 cell line. CMIT markedly inhibited phagocytic oxidative burst as measured by zymosan-induced chemiluminescence, and cellular cytokine secretion as measured by zymosan-induced TNF-α secretion. The 50% inhibition concentration (LC(50)) for CMIT was 0.002-0.004 mM for both cellular functions. AM exposed to CMIT for as little as 2 min showed markedly inhibited functions that persisted for at least 5 h. Sodium metabisulfite was able to partially neutralize the inhibitory activity of CMIT. Cysteine and glutathione, when present at a molar ratio of 2-1 or higher against CMIT, were effective neutralizers, while serine, histidine, alanine, and albumin were without effect. When the AM testing system was used to compare the toxicity of CMIT against three other candidate biodiesel biocides, methylene dithiocyanate (MDC) was found to be of comparable toxicity to CMIT, 2-methyl-4-isothiazolin-3-one (MIT) was much less toxic, and dimethyl acetylenedicarboxylate (DMAD) was non-toxic. Because AM is among the first cell-type exposed to inhaled biodiesel aerosols, the result suggested that CMIT present in biodiesel may produce respiratory effects, and further investigations including animal studies are warranted.