Properties and flame retardancy of polylactide composites incorporating tricresyl phosphate and modified microcrystalline cellulose from oil palm empty fruit bunch waste.

One of the major environmental issues that have an impact on humans, animals, and their surroundings is plastic garbage. The use of biodegradable polymers in place of traditional plastics is one of the best solutions to this significant issue. The bio-circular-green (BCG) economic model is supported by the use of microcrystalline cellulose (MCC) as a bio-filler for polylactide (PLA) composites, which may also help to address the issue of improper plastic waste management. This study explores the chemical modification of MCC derived from oil palm empty fruit bunch waste (OPMC). Maleic anhydride-modified OPMC (MAMC) is successfully synthesized by a solvent-free and low temperature heating procedure. MAMC and tricresyl phosphate (TCP) were used as additives in PLA composites which were processed by melt extrusion and compression molding. Characterization studies confirmed the successful modification of MAMC and indicated that TCP played a crucial role as an effective plasticizer and flame retardant for PLA. All PLA/TCP composites showed significantly improved toughness and delayed ignition. The appropriate TCP level was 10 phr. The incorporation of TCP and MAMC resulted in a synergistic enhancement of impact strength and maintained excellent flame inhibition. Moreover, the thermal stability of the PLA composites increased with increments of MAMC.

Synergistic effect of microcrystalline cellulose from oil palm empty fruit bunch waste and tricresyl phosphate on the properties of polylactide composites.

Microcrystalline cellulose (MCC) was extracted from oil palm empty fruit bunch (OPEFB) waste by integrated chemical treatments of delignification, bleaching, and acidic hydrolysis. The obtained MCC (OPMC) and tricresyl phosphate (TCP) were used as additives for polylactide (PLA) composites. The influences of OPMC and TCP contents, separately and in combination, were evaluated on the properties of the composites. Characterization studies confirmed the successful extraction of OPMC from OPEFB waste. With regard to the properties of the PLA composite, the appropriate content of OPMC should be 5 phr. The good distribution of OPMC in the polymer matrix changed the failure behavior of the composite from brittle to ductile. All the PLA composites with TCP and OPMC showed flame inhibition and retarded ignition. The synergistic effect of TCP and OPMC resulted in outstanding improvement of impact strength and flame retardancy of composites. The impact toughness of PT10M5 increased to about 218.4 % and 72.3 % that of neat PLA and PT0M5, respectively. Moreover, PT10M5 achieved V-0 rating with high LOI (38.5 %). All these characteristics promise extended applications for PLA composite in bio, circular, and green (BCG) economies and electronics industries.

Biodegradation of tricresyl phosphates isomers by a novel microbial consortium and the toxicity evaluation of its major products.

A novel microbial consortium ZY1 capable of degrading tricresyl phosphates (TCPs) was isolated, it could quickly degrade 100% of 1 mg/L tri-o-cresyl phosphate (ToCP), tri-p-cresyl phosphate (TpCP) and tri-m-cresyl phosphate (TmCP) within 36, 24 and 12 h separately and intracellular enzymes occupied the dominated role in TCPs biodegradation. Additionally, triphenyl phosphate (TPHP), 2-ethylhexyl diphenyl phosphate (EHDPP), bisphenol-A bis (diphenyl phosphate) (BDP), tris (2-chloroethyl) phosphate (TCEP) and tris (1-chloro-2-propyl) phosphate (TCPP) could also be degraded by ZY1 and the aryl-phosphates was easier to be degraded. The TCPs reduction observed in freshwater and seawater indicated that high salinity might weak the degradability of ZY1. The detected degradation products suggested that TCPs was mainly metabolized though the hydrolysis and hydroxylation. Sequencing analysis presented that the degradation of TCPs relied on the cooperation between sphingobacterium, variovorax and flavobacterium. The cytochrome P450/NADPH-cytochrome P450 reductase and phosphatase were speculated might involve in TCPs degradation. Finally, toxicity evaluation study found that the toxicity of the diesters products was lower than their parent compound based on the generation of the intracellular reactive oxygen (ROS) and the apoptosis rate of A549 cell. Taken together, this research provided a new insight for the bioremediation of TCPs in actual environment.

Photochemical reaction of tricresyl phosphate (TCP) in aqueous solution: Influencing factors and photolysis products.

Organophosphate triesters (OPEs) have caused great concern as a class of emerging environmental contaminants due to their widespread use and their toxicity to organisms. However, the phototransformation behavior of OPE is still not fully understood, which is important for understanding their environmental fate. In the present study, the photodegradation of tricresyl phosphate (TCP), one of the most widely detected OPEs in aqueous environments, was investigated including the direct photolysis and in the presence of several natural water factors, NO2-, Fe3+ and humic acid. The degradation process followed the pseudo-first-order kinetics, with rate constant increasing slightly with increasing initial TCP concentration. The presence of NO2- and Fe3+ was observed to promote the photochemical loss of TCP, while humic acid played a negative role on TCP transformation. Electron spin resonance (EPR) analysis showed that carbon-centered radical was produced in the photolysis process of TCP, and hydroxyl radical contributed to the promotion of rate constant for Fe3+ and NO2-. Four photolysis products were tentatively identified by HPLC-LTQ-Orbitrap MS analysis, and the possible degradation pathways of TCP were proposed. These findings provide a meaningful reference for the fate and transformation of OPEs in natural water.

Different organophosphate flame retardant and metabolite concentrations in urine from male and female university students in Beijing and an assessment of exposure via indoor dust.

Organophosphate flame retardants (OPFRs) have been found in human samples and associated with adverse health effects. In the present study, OPFR and dialkyl and diaryl phosphate (DAP) concentrations in human urine were determined and differences in the concentrations in urine from males and females were investigated. Urine samples from 22 male and 26 female university students, paired dust samples from the dormitories (13 each for males and females), and 10 dust samples from university teaching buildings were analyzed. The tri-o-cresyl phosphate (TOCP), tri-p-cresyl phosphate (TPCP), and tris(2-chloroisopropyl)phosphate (TCIPP) concentrations were significantly higher (p = 0.049, 0.023, and 0.027, respectively) in urine from the female students than in urine from the male students. Similar differences were found between males and females in terms of OPFR exposure and OPFR concentrations in urine for three-fourths of the OPFRs. Questionnaire answers and calculations indicated that disparities in OPFR concentrations in urine were mainly caused by females spending much more time than males in dormitories. Organophosphate flame retardants may pose degrees of health risk similar to those of polybrominated diphenyl ethers (PBDEs), and this must be considered when making decisions about controlling flame retardants. We are not aware of any previous studies that simultaneously monitor OPFRs and DAPs in human urine in China. Environ Toxicol Chem 2019;38:760-768. © 2019 SETAC.

Investigating the potential for transisomerisation of trycresyl phosphate with a palladium catalyst and its implications for aircraft cabin air quality.

The quality of aircraft cabin air has been an area of concern for several decades. Many investigations have linked the presence of organophosphates in air to Aerotoxic Syndrome with adverse symptoms reported by thousands of aircraft crew across the globe. Currently the source of organophosphates has been under debate, with studies pointing towards tricresylphosphates (TCP) in aircraft oil as the main source due to leaks in engine seals resulting in fumes entering the cabin. However, comparisons of oil and cabin samples have shown that the cabin samples contain a much higher proportion of ortho-substituted TCP than is commonly detected in oil. The aim of this experiment was to investigate the potential for palladium catalysts (present in aircraft air conditioning systems) to convert meta- and para-substituted TCP to produce ortho-substituted TCP through transisomerisation. This experiment was performed in a controlled laboratory setting aimed to represent the conditions likely to be experienced in aircraft. Samples were introduced to a stainless steel micro reactor tube containing the pelletized palladium catalyst using a HPLC pump with a 0.2 ml/min feed flow rate. The temperature maintained at 400 °C over a period of 1 h and samples collected using a condensing vesicle. These were then diluted and transferred to a 2 mL vial for analysis by gas chromatography mass spectrometry. No evidence supporting the transisomerisation of tricresylphosphate was obtained. This indicates that more emphasis should be placed on identifying other potential sources of ortho substituted TCP.

Kinetics and mechanism of OH-initiated atmospheric oxidation of organophosphorus plasticizers: A computational study on tri-p-cresyl phosphate.

Understanding the atmospheric fate of organophosphorus plasticizers is important for their environmental risk assessment. However, limited information is available at present. In this study, density functional theory (DFT) calculations were performed to investigate the transformation mechanism and kinetics of tri-p-cresyl phosphate (TpCP) initiated by OH. Results show that the initial reactions are dominated by H-abstraction and OH addition to form TpCP-radical, TpCP-OH adducts and aryl phosphodiester. The H-abstraction pathways are more favorable than the OH addition pathways. The TpCP-radical and TpCP-OH adducts can further react with O2 in the atmosphere to finally form benzaldehyde phosphate, hydroxylated TpCP and bicyclic radicals. Based on the transition state theory, the calculated rate constant (kOH) of TpCP with OH at T = 298 K is 1.9 × 10-12 cm3molecule-1s-1 with an atmospheric lifetime of 4.2 days, which demonstrates that gaseous TpCP is atmospherically persistent. This study provides a comprehensive investigation of the OH-initiated oxidation of TpCP, which is useful for understanding its mechanism of transformation and evaluating the risk in atmospheric environment.

A comparison of fresh and used aircraft oil for the identification of toxic substances linked to aerotoxic syndrome.

Fresh and used aircraft engine lubricants (Mobil Jet Oil II) were analysed using a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer (FTICRMS) and comprehensive two dimensional gas chromatography with high resolution time of flight mass spectrometry (GCxGC-HRTOFMS). The composition of the fresh oil was established, with special focus to its tricresyl phosphate (TCP) content as this has formed the focus for most investigations into aerotoxic syndrome. The results showed that only four TCP isomers were present at detectable levels in the fresh oil: mmm-TCP, mmp-TCP, ppm-TCP and ppp-TCP. The results indicate that the formulation of Mobile Jet Oil II does not contain the more toxic ortho substituted TCP isomers at concentrations above 0.0005%. The temperatures of jet engines during operation are greater than 200 °C which creates the potential to alter the composition of the original oil and create other toxic compounds. The results show there may be a significant risk from alkylated cresyl phosphates, which were identified in the used oils at concentrations calculated in the range of 0.13-0.69%. w/w. Several xylenyl and ethylphenyl phosphates have been shown to exhibit a similar toxicity to ortho substituted TCP isomers which makes there discovery in used oil significant. These compounds should be included in future aircraft air quality studies and when assessing the risks and causes of aerotoxic syndrome.

Tricresyl phosphate and the aerotoxic syndrome of flight crew members--current gaps in knowledge.

Tricresyl phosphate (TCP), and in particular its tri-ortho substituted isomer (o,o,o-TCP), has been frequently used in aircraft engine oil. Bleed air, provided to the flight deck and cabin can contain traces of TCP. TCP can cause neurotoxic effects in humans. Regularly, airline pilots complain about loss of memory, headaches, dizziness, tunnel vision and other neurotoxic effects. The concentrations of TCP reported in flight deck air (max. ca. 50-100 ng m(-3) total TCP) do not exceed provisional toxicity thresholds. These thresholds, however, contain a very high uncertainty and need further underpinning. The many non-detects and relatively low TCP concentrations reported suggest that TCP on its own is not likely to be responsible for the reported health problems of pilots. Specific conditions in air planes and other toxic compounds present in bleed air, whether or not in combination with TCP, may be responsible for the reported neurotoxic syndromes. Sensitivity of individuals seems to be an important factor as well. The clinical signs observed with a selected group of pilots are serious enough to call for further elucidation of this issue.

Determination of tricresyl phosphate air contamination in aircraft.

Monitoring of tricresyl phosphate (TCP) contamination of cockpit air was undertaken in three types of military aircraft [fighter trainer (FT), fighter bomber (FB), and cargo transport (CT) aircraft]. The aircraft had a previous history of pilot complaints about cockpit air contamination suspected to originate from the engine bleed air supply through the entry of aircraft turbine engine oil (ATO) into the engine compressor. Air samples were collected in flight and on the ground during engine runs using sorbent tubes packed with Porapak Q and cellulose filters. A total of 78 air samples were analysed, from 46 different aircraft, and 48 samples were found to be below the limit of detection. Nine incidents of smoke/odour were identified during the study. The concentrations of toxic o-cresyl phosphate isomers were below the level of detection in all samples. The highest total TCP concentration was 51.3 µg m(-3), while most were generally found to be <5 µg m(-3) compared with the 8-h time-weighted average exposure limit of 100 µg m(-3) for tri-o-cresyl phosphate. The highest concentrations were found at high engine power. Although TCP contamination of cabin/cockpit air has been the subject of much concern in aviation, quantitative data are sparse.

Exposure to tri-o-cresyl phosphate detected in jet airplane passengers.

The aircraft cabin and flight deck ventilation are supplied from partially compressed unfiltered bleed air directly from the engine. Worn or defective engine seals can result in the release of engine oil into the cabin air supply. Aircrew and passengers have complained of illness following such "fume events". Adverse health effects are hypothesized to result from exposure to tricresyl phosphate mixed esters, a chemical added to jet engine oil and hydraulic fluid for its anti-wear properties. Our goal was to develop a laboratory test for exposure to tricresyl phosphate. The assay was based on the fact that the active-site serine of butyrylcholinesterase reacts with the active metabolite of tri-o-cresyl phosphate, cresyl saligenin phosphate, to make a stable phosphorylated adduct with an added mass of 80 Da. No other organophosphorus agent makes this adduct in vivo on butyrylcholinesterase. Blood samples from jet airplane passengers were obtained 24-48 h after completing a flight. Butyrylcholinesterase was partially purified from 25 ml serum or plasma, digested with pepsin, enriched for phosphorylated peptides by binding to titanium oxide, and analyzed by mass spectrometry. Of 12 jet airplane passengers tested, 6 were positive for exposure to tri-o-cresyl phosphate that is, they had detectable amounts of the phosphorylated peptide FGEpSAGAAS. The level of exposure was very low. No more than 0.05 to 3% of plasma butyrylcholinesterase was modified. None of the subjects had toxic symptoms. Four of the positive subjects were retested 3 to 7 months following their last airplane trip and were found to be negative for phosphorylated butyrylcholinesterase. In conclusion, this is the first report of an assay that detects exposure to tri-o-cresyl phosphate in jet airplane travelers.

Determination of ortho-cresyl phosphate isomers of tricresyl phosphate used in aircraft turbine engine oils by gas chromatography and mass spectrometry.

Tricresyl phosphate (TCP) is used as an anti-wear additive in aircraft turbine engine oil. Concerns about its toxicity are largely based on the tri-o-cresyl phosphate isomer content. However, the presence of other and more toxic isomers has been previously suggested. In this work, the structural isomers of TCP have been determined by two methods (experimental and semi-theoretical). First, the TCP isomers were separated by gas chromatography (GC) and identified by mass spectrometry (MS). Second, after base cleavage of TCP, GC was used to quantify the cresol precursors. These results were used to calculate the TCP isomer distribution based on the assumption of a statistical distribution of the TCP isomers. The results from the two determinations showed reasonable agreement for three of the four oils studied. The o-cresyl isomers were found to be present almost exclusively as the more toxic mono-o-cresyl isomers in the concentration range 13-150 mg/L. The ability to analyse for the mono-o-cresyl isomers allows the toxicity of TCP to be based on the latter isomers rather than on the less toxic tri-o-cresyl phosphate isomer.

[Tricresyl phosphate residue in garland chrysanthemum and its origin].

Unknown peaks were detected in the chromatogram of garland chrysanthemum extract in analysis of organophosphorus pesticide residues. The unknown peaks were identified as isomers of tricresyl phosphate (TCP) by GC/MS. TCP is used as a plasticizer in polyvinyl chloride, and there is no report of its detection in foods. Therefore, we investigated the origin of TCP detected in garland chrysanthemum. We found no effect of contact with packaging film or polyvinyl chloride sheet used in greenhouses. However, TCP was detected at 0.03 microg/g (average) in 16 of 20 samples of garland chrysanthemum that had been in contact with polyvinyl chloride tubing used for warming greenhouses. These results indicate that TCP migrated to the garland chrysanthemum from the tubing used to keep greenhouses warm.

[Determination method of tricresyl phosphate in polyvinyl chloride].

A simple and rapid method using HPLC was developed for the determination of tricresyl phosphate (TCP) in polyvinyl chloride (PVC) articles. A test sample was extracted with acetonitrile at 37 degrees C overnight. The extract solution diluted with an equivalent amount of water was applied to a Sep-Pak C18 cartridge, and TCP was eluted with acetonitrile-water (2:1) mixture. The eluate was analyzed by HPLC with an Inertsil Ph-3 column, using 65% acetonitrile/water as the mobile phase, with UV detection (264 nm). The calibration curve was rectilinear from 0.5 to 100 micrograms/mL. The recoveries of TCP added to various kinds of PVC articles at the level of 1,000 micrograms/g were 84.7-98.6%. The determination limit of TCP was 50 micrograms/g in samples. This method was applied to products including 3.1, 6.6 and 8.8% TCP and the recoveries of TCP were 87.3-91.4%. This method is very simple, and it seems suitable for a regulatory test.

Degradation of organophosphoric esters in leachate from a sea-based solid waste disposal site.

Degradation of organophosphoric esters (OPEs) in leachate from a sea-based solid waste disposal site was investigated by laboratory experiment. Aryl-phosphates, tricresyl phosphate and triphenyl phosphate, in leachate rapidly decreased to less than the detection limit within 20 days under aerobic condition, suggesting high biodegradability. These phosphates also decreased in sterilized leachate, which suggested a contribution to degradation by reactions (adsorption and chemical degradation) with chemicals in the leachate. Concerning alkyl-phosphates, tributyl phosphate decreased rapidly after one week, which is considered to have been caused by biodegradation. Tris-2-ethylhexyl phosphate and tris-2-butoxyethyl phosphate decreased slowly in all samples but that of sterilized distilled water. This however, suggested contribution of biodegradation because the velocity of decrease in the leachate was higher than in control samples. Among chloro alkylphosphates, decrease of tris-2-chloroethyl phosphate and tris-dichloropropyl phosphate were observed though it was not obvious whether by biodegradation or not. Decrease of tris-2-chloropropyl phosphate (TCPP) was not observed for 80 days suggesting that TCPP remains in the leachate over a long period of time. Except for aryl-phosphates decrease of OPEs was not observed under anaerobic condition. It was considered that the composition ratio and the behavior of OPEs in leachate in the field reflects the biological and chemical degradation as well as the chemical properties of OPEs.

Detection of tricresyl phosphates and determination of tri-o-cresyl phosphate in edible oils.

Tricresyl phosphate (TCP) in contaminated edible oils was extracted using acetonitrile and detected by thin layer chromatography as well as gas chromatography (GC). The chromatoplate was developed with isooctane-ethyl acetate (90 + 10) and visualized by spraying with 2,6-dichloroquinone chloroimide. TCP gives a characteristic blue-violet spot when heated at 100 degrees C for 15 min. The method is direct and sensitive and can be used to detect as low as 2.5 micrograms TCP or TOCP (tri-o-cresyl phosphate). GC was carried out using 10% OV-101 as the stationary phase and flame ionization detection for confirmation and quantitation of TOCP in oils.

Extraction and cleanup of fish, sediment, and water for determination of triaryl phosphates by gas-liquid chromatography.

Several techniques were evaluated for extracting triphenyl phosphate (TPP), 14C-labeled TPP, cresyl diphenyl phosphate, and tricresyl phosphate isomers (o-TCP, m-TCP, and p-TCP) from fish and sediment samples. Extracts of fish samples were cleaned up by gel permeation chromatography/alumina column chromatography; sediment extracts received alumina treatment only. Compounds were determined by gas-liquid chromatography (GLC) with nitrogen-phosphorus detection. Methanol/Polytron and hexane/ball mill extraction of fish samples fortified at 0.01, 0.1, and 1.0 microgram/g levels gave overall recoveries of the 5 compounds of 89 and 97%, respectively. Methanol recovered more radioactivity (97%) from fish exposed to 14C-TPP in aquaria for 24 h than did hexane from fish exposed for 16 h (79%). Refluxing fortified sediment (0.05 and 0.5 microgram/g) with methanol-water (9 + 1) gave significantly higher recoveries (88%) of the 5 triaryl phosphates than did dichloromethane-methanol (1 + 1) reflux or acetone-hexane (1 + 1) Soxhlet extraction. Recoveries of TPP and o-, m- and p-TCP from fortified river water (0.5, 5.0, and 50 microgram/L) by shaking with dichloromethane ranged from 91 to 118%. Some problems were encountered with interfering GLC peaks at low (microgram/g) levels in fish and sediment extracts despite the use of nitrogen-phosphorus specific detectors.