Phthalate plasticizers: accumulation and effects on weight and food consumption in captive starlings

PHTHALATE ESTERS (PLASTICIZERS) IN THE UROPYGIAL GLAND AND THEIR RELATIONSHIP TO PLASTICS INGESTION IN SEABIRDS ALONG THE COAST OF ESPÍRITO SANTO, EASTERN BRAZIL

Plastic ingestion is a problem for seabirds worldwide. In addition to direct health effects such as obstruction or perforation of the gastrointestinal tract, plastic ingestion can also lead to indirect health effects through the release of chemicals that may be absorbed and cause systemic and chronic toxicity. Among chemicals that can be released by plastics are phthalate esters, a group of chemicals widely used as plasticizers or additives to change the physical characteristics of plastics. In this study, three phthalate esters, dimethyl phthalate (DMP), dibuthyl phthalate (DBP), and diethylhexyl phthalate (DEHP), were quantified in the uropygial gland of 48 seabirds from 16 species collected ashore in a tropical region, the coast of Espírito Santo, Eastern Brazil. Including trace levels, DMP was detected in 16 birds (33%) from 10 species, with an average concentration of 0.014 ± 0.005 ng/µl (mean ± SD for individuals with concentrations above the practical level of detection of 0.01 ng/µl). DBP was detected in 15 birds (31%) from 11 species, with an average concentration of 0.049 ± 0.032 ng/µl. DEHP was detected in 21 birds (44%) from 11 species, with an average concentration of 0.115 ± 0.105 ng/µl. DMP concentration in the uropygial gland was positively associated with the presence, number, and mass of plastic items in the upper digestive tract. However, no such relationship was noted for DBP nor DEHP, suggesting the concentration of phthalate compounds in the uropygial gland might not always serve as a reliable proxy for plastic ingestion. In spite of relatively high frequencies of detection, the low concentrations of phthalates detected in this study suggest levels of exposure below known toxicity thresholds. Further studies on the potential adverse effects of phthalate exposure in seabirds are necessary, especially on the reproductive development of embryos and chicks.

Birds and plastic pollution: recent advances

Plastic waste and debris have caused substantial environmental pollution globally in the past decades, and they have been accumulated in hundreds of terrestrial and aquatic avian species. Birds are susceptible and vulnerable to external environments; therefore, they could be used to estimate the negative effects of environmental pollution. In this review, we summarize the effects of macroplastics, microplastics, and plastic-derived additives and plastic-absorbed chemicals on birds. First, macroplastics and microplastics accumulate in different tissues of various aquatic and terrestrial birds, suggesting that birds could suffer from the macroplastics and microplastics-associated contaminants in the aquatic and terrestrial environments. Second, the detrimental effects of macroplastics and microplastics, and their derived additives and absorbed chemicals on the individual survival, growth and development, reproductive output, and physiology, are summarized in different birds, as well as the known toxicological mechanisms of plastics in laboratory model mammals. Finally, we identify that human commensal birds, long-life-span birds, and model bird species could be utilized to different research objectives to evaluate plastic pollution burden and toxicological effects of chronic plastic exposure.

Fish and Seabird Gut Conditions Enhance Desorption of Estrogenic Chemicals from Commonly-Ingested Plastic Items

Plastic is ingested by over 100 bird species and 40 fish species. Once ingested, plastic may release endocrine-disrupting plastic additives in the animal; however, amounts transferred are poorly characterized. We exposed 16 commonly ingested plastic items to fish and seabird laboratory gut mimic models using the digestive enzyme pepsin at pH 2 and shook them for 16 h at either 28 °C (in saltwater) for fish or 40 °C (in freshwater) for seabirds. Gut liquid was then evaluated for estrogen receptor activity using an in vitro cell line, and plastic-additive concentrations were quantified using ultrahigh-performance liquid chromatography/tandem mass spectrometry. Both seabird ( p < 0.0001) and fish gut conditions ( p < 0.0001) significantly enhanced the biological estrogenicity of expanded polystyrene, polyethylene shopping bag, and polypropylene string relative to controls, resulting in up to a 10.6-fold increase in estrogenicity. Out of 12 plastic additives analyzed, bisphenol A (BPA) (204 ± 129%) and diethylhexyl phthalate (DEHP) (175 ± 97%) concentrations were significantly increased in seabird gut conditions relative to control and butylbenzyl phthalate (BBP) (132 ± 68%) was significantly increased in fish gut conditions relative to control. BPA, DEHP, and BBP did not adequately account for the increase in biological estrogenicity, suggesting that uncharacterized plastic additives may have been enhanced by gut conditions.