Degradation of Various Plastics in the Environment

It is very important to understand the interaction between plastics and environment in ambient conditions. The plastics degrade because of this interaction and often their surface properties change resulting in the creation of new functional groups. The plastics after this change continue to interact with the environment and biota. It is a dynamic situation with continuous changing parameters. Polyethylene, polypropylene, and polyethylene terephthalate (PET) degrade through the mechanisms of photo-, thermal, and biodegradation. The three polymers degrade with different rates and different pathways. Under normal conditions, photo- and thermal degradation are similar. For polyethylene, photo-degradation results in sharper peaks in the bands which represent ketones, esters, acids, etc. on their infrared spectrum. The same is true for poly propylene but this polymer is more resistant to photo-degradation. The photo-oxidation of PET involves the formation of hydroperoxide species through oxidation of the CH2 groups adjacent to the ester linkages and the hydroperoxides species involving the formation of photoproducts through several pathways. For the three polymers, interaction with microbes and formation of biofilms are different. Generally, biodegradation results in the decrease of carbonyl indices if the sample has already been photo-degraded by exposure to UV. Studies with environmental samples agree with these findings but the degradation of plastics is very subjective to the local environmental conditions that are usually a combination of those simulated in laboratory conditions. For example, some studies suggested that fragmentation of plastic sheet by solar radiation can occur within months to a couple of years on beaches, whereas PET bottles stay intact over 15 years on sea bottoms.

Kalliopi N. Fotopoulou, Hrissi K. Karapanagioti, Chapter, Part of the series The Handbook of Environmental Chemistry, pp 1-22, Date: 13 April 2017

The chapter

The presence of microplastics in commercial salts from different countries

The occurrence of microplastics (MPs) in saltwater bodies is relatively well studied, but nothing is known about their presence in most of the commercial salts that are widely consumed by humans across the globe. Here, we extracted MP-like particles larger than 149 μm from 17 salt brands originating from 8 different countries followed by the identification of their polymer composition using micro-Raman spectroscopy. Microplastics were absent in one brand while others contained between 1 to 10 MPs/Kg of salt. Out of the 72 extracted particles, 41.6% were plastic polymers, 23.6% were pigments, 5.50% were amorphous carbon, and 29.1% remained unidentified. The particle size (mean ± SD) was 515 ± 171 μm. The most common plastic polymers were polypropylene (40.0%) and polyethylene (33.3%). Fragments were the primary form of MPs (63.8%) followed by filaments (25.6%) and films (10.6%). According to our results, the low level of anthropogenic particles intake from the salts (maximum 37 particles per individual per annum) warrants negligible health impacts. However, to better understand the health risks associated with salt consumption, further development in extraction protocols are needed to isolate anthropogenic particles smaller than 149 μm.

Ali Karami, Abolfazl Golieskardi, Cheng Keong Choo, Vincent Larat, Tamara S. Gallowa & Babak Salamatinia, Scientific Reports 7, Article number: 46173 (2017)

The article

Toxic effects of polyethylene terephthalate microparticles and Di(2-ethylhexyl)phthalate on the calanoid copepod, Parvocalanus crassirostris

Large amounts of plastic end up in the oceans every year where they fragment into microplastics over time. During this process, microplastics and their associated plasticizers become available for ingestion by different organisms. This study assessed the effects of microplastics (Polyethylene terephthalate; PET) and one plasticizer (Di(2-ethylhexyl)phthalate; DEHP) on mortality, productivity, population sizes and gene expression of the calanoid copepod Parvocalanus crassirostris. Copepods were exposed to DEHP for 48 h to assess toxicity. Adults were very healthy following chemical exposure (up to 5120 µg L−1), whereas nauplii were severely affected at very low concentrations (48 h LC50value of 1.04 ng L−1). Adults exposed to sub-lethal concentrations of DEHP (0.1–0.3 µg L−1) or microplastics (10,000–80,000 particles mL−1) exhibited substantial reductions in egg production. Populations were exposed to either microplastics or DEHP for 6 days with 18 days of recovery or for 24 days. Populations exposed to microplastics for 24 days significantly depleted in population size (60±4.1%, p<0.001) relative to controls, whilst populations exposed for only 6 days (with 18 days of recovery) experienced less severe depletions (75±6.0% of control, p<0.05). Populations exposed to DEHP, however, exhibited no recovery and both treatments (6 and 24 days) yielded the same average population size at the termination of the experiment (59±4.9% and 59±3.4% compared to control; p<0.001). These results suggest that DEHP may induce reproductive disorders that can be inherited by subsequent generations. Histone 3 (H3) was significantly (p<0.05) upregulated in both plastic and DEHP treatments after 6 days of exposure, but not after 18 days of recovery. Hsp70-like expression showed to be unresponsive to either DEHP or microplastic exposure. Clearly, microplastics and plasticizers pose a serious threat to zooplankton and potentially to higher trophic levels.

Franz M. Heindler, Fahad Alajmi, Roger Huerlimann, Chaoshu Zeng, Stephen J. Newman, George Vamvounis, Lynne van Herwerden, Ecotoxicology and Environmental Safety, Volume 141, July 2017, Pages 298–305

The article

Phthalate metabolites in the European eel (Anguilla anguilla) from Mediterranean coastal lagoons

The levels and fate of phthalate metabolites have been poorly evaluated in fish, despite their potential ecotoxicological impacts. The present study aims to characterize the levels of phthalate metabolites in muscle tissue of yellow eels (Anguilla anguilla) from two coastal Mediterranean lagoons, during three sampling periods. Nine phthalate metabolites were detected in > 70% of the samples. Slightly higher levels of phthalate metabolites were detected in March and June compared to October, suggesting possible seasonal variations in environmental release and/or phthalate metabolization process by eels. The large sample size (N = 117) made it possible to explore correlations between phthalate metabolites’ levels and individual parameters, such as body length, age, body condition and hepatic histo-pathologies. Body length and estimated age poorly correlated with phthalate metabolites, suggesting that eels did not accumulate phthalates during growth, contrary to persistent compounds. Eels presented different grades of hepatic fibrosis and lipidosis. A negative correlation was found between the severity of these pathologies in the liver and the sum of phthalate metabolites levels, supporting the hypothesis that eels with damaged liver are less able to metabolize xenobiotics.

C. Fourgous, M. Chevreuil, F. Alliot, E. Amilhat, E. Faliex, S. Paris-Palacios, M.J. Teil, A. Goutte, Science of The Total Environment, Volumes 569–570, 1 November 2016, Pages 1053–1059

The article

Phthalates and perfluorinated alkylated substances in Atlantic bluefin tuna (Thunnus thynnus) specimens from Mediterranean Sea (Sardinia, Italy): Levels and risks for human consumption

Atlantic blue fin tuna (Thunnus thynnus) is a species of great importance for Mediterranean Sea area, from both ecological and commercial points of view. The scientific literature reports few data on the contamination of this fish by emerging organic compounds such as perfluorinated alkylated substances(PFASs) and phthalates, being the latter never been studied in tuna. This study therefore investigated the presence of the PFASs perfluorooctane sulphonate (PFOS) and perfluoroctanoic acid (PFOA) and the phthalate di-2-ethylhexyl phthalate (DEHP), also monitored by its metabolite mono-2-ethylhexyl phthalate(MEHP), to assess both the state of contamination of Atlantic bluefin tuna specimen and the risk due to the toxicity of these compounds for human consumption. While PFOA was never found, detectable levels of PFOS (0.4–1.88 ng/g), DEHP (9–14.62 ng/g) and MEHP (1.5–6.30 ng/g) were found. The results were elaborated relating the accumulation to the size and age of the individuals and showed a correlation between the levels of different pollutants investigated.

Cristiana Guerranti, Alessandro Cau, Monia Renzi, Simone Badini, Eleonora Grazioli, Guido Perra & Silvano Ettore Focardi, Journal of Environmental Science and Health, Part B, Volume 51, 2016 – Issue 10

The article

Detection of phthalate esters in seawater by stir bar sorptive extraction and gas chromatography–mass spectrometry

We developed the stir bar sorptive extraction (SBSE)–gas chromatography–mass spectrometry (GC–MS) method to detect 15 kinds of PAEs in seawater. The stir bars (20 mm in length and 1 mm in film thickness) coated with 150 μL of polydimethylsiloxane (PDMS) were found to demonstrate the optimal extraction of PAEs. The optimal conditions were as follows: extraction time of 2 h, extraction temperature of 25 °C, sodium chloride of 5%, methanol of 10%, analytical time of 50 min, and methanol–acetonitrile (4:1) as the solvent. SBSE–GC–MS revealed that under the set temperature, the chromatographic peaks of all 15 PAEs can appear with complete separation. The detection limit ranged from 0.07 μg/L to 5.71 μg/L, whereas the limit of quantification ranged from 0.023 μg/L to 193 μg/L, and the correlation coefficients between the chromatographic peak area and concentration of the PAEs were greater than 0.92.

Qingqing Si, Fengmin Li, Chenchen Gao, Cong Wang, Zhenyu Wang, Jian Zhao, Marine Pollution Bulletin, Volume 108, Issues 1–2, 15 July 2016, Pages 163–170

The article

Tissue Phthalate Levels Correlate With Changes in Immune Gene Expression in a Population of Juvenile Wild Salmon

Phthalates have detrimental effects on health and have been shown to dysregulate the immune system of mammals, birds, and fish. We recently reported that di(2-ethylhexyl) phthalate exposure reduces the abundance and inhibits the proliferation of rainbow trout (Oncorhynchus mykiss) IgM+ B lymphocytes and expression of secreted immunoglobulin heavy-chain mu transcripts in an in vitro culture system. We proposed that phthalates act as immunomodulators by modifying the normal B cell-activation pathways by accelerating B cell differentiation while suppressing plasmablast expansion, thus resulting in fewer IgM-secreting plasma cells. This hypothesis was tested here in an in vivo field study of juvenile Dolly Varden (Salvelinus malma) from a plastic-polluted lake in the Gulf of Alaska. Fish tissues were analyzed for both phthalate levels using liquid chromatography-coupled tandem mass spectrometry and for changes in immune gene expression using reverse transcriptase-real time polymerase chain reaction. Results showed that fish with higher tissue levels of di(2-ethylhexyl) phthalate, di(n-butyl) phthalate, and/or dimethyl phthalate expressed significantly fewer secreted and membrane-bound immunoglobulin heavy-chain mu and Blimp1 transcripts in their hematopoietic tissue. This suggests that in vivo uptake of phthalates in fish changes the expression of B cell-specific genes. Chronic exposure to phthalates likely dysregulates normal B-lymphoid development and antibody responses in salmonids and may increase susceptibility to infection. Given the conserved nature of B-lineage cells in vertebrate animals, other marine species may be similarly affected by chronic phthalate exposure.

Kelly Martins, Birgit Hagedorn, Shareen Ali, John Kennish, Ben Applegate, Matthias Leu, Lidia Epp, Chris Pallister, Archives of Environmental Contamination and Toxicology, July 2016, Volume 71, Issue 1, pp 35–47

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