# Reality Check: Experimental Studies on Microplastics Lack Realism
## 6 Leached Chemicals
### Aquatic Effects
They acknowledged that changes they observed could have been caused by mechanical damage or leached chemicals, or both. They mentioned that some textile dyes, namely benzothiazoles ([PERSON] et al., 2015), induced gill alterations in fish that resemble those they observed from mf exposure [74]. Similarly, [PERSON] et al. (2014) exposed adult medaka (_Oryza latipes_) to polyethylene MPs and found changes in estrogen receptor-mediated gene expression and histopathology of the testes, implying altered endocrine function [75]. These effects resemble those caused by the plastic additives di-(2-ethylhexyl)-phthalate (DEHP) and its metabolite mono(2-ethylhexyl)-phthalate (MEHP) in the medaka [76]. MP studies on the lugworm, _Arenicola marina_ included transfer of PCBs (polychlorinated biphenyls) from polystyrene (PS) MPs [77]. Effects on survival, activity, and bodyweight, and the transfer of PCBs were assessed. The concentration of MPs in the spiked sediment was directly related to the uptake of MPs and to weight loss. Reduced feeding was observed at a dose of 7.4% dry weight. There were statistically significant effects on bioaccumulation and fitness, but the magnitude of effects was small. However, in similar studies, polyethelene MPs (PE) did not act as a measurable vector of PCBs [77]. [PERSON] et al. (2013) exposed lugworms (_Arenicola marina_) to sand with 5% PVC MP that was spiked with the pollutants nonylphenol and phenanthrene and additive chemicals tridosan and PBDE-47 [69]. The pollutants and the additives were found to be transferred into gut tissues and to cause some biological effects. However, sand transferred greater amounts of the pollutants to the worms than did MPs. Uptake of nonylphenol from MPs or sand reduced the ability to remove pathogenic bacteria. Uptake of Triclosan from PVC reduced the worms' ability to burrow and engineer sediments and caused mortality (both by >55%) while PVC alone made the lugworms more susceptible to oxidative stress. In contrast, some studies have found that chemicals bind so tightly to MPs that the overall bioavailability is reduced and that there is less transfer of toxic chemicals from ingested plastics than from sediments, indicating that plastic is a less important source of contaminants to animals [78; 79; 80]. Herring (_Clupea harengus_) larvae were tube-fed a dose of up to 200 MP spheres spiked with \({}^{14}\)C-labelled PCB-153 while control larvae were tube-fed an isotonic solution without MPs [81]. Most larvae evacuated all or almost all MPs by 24 h and tracer levels in exposed fish were not significantly different from control larvae. There was no significant transfer observed of PCB from MPs into larvae which had gut-transit times of <24 h. [PERSON] et al. (2014) assessed the potential of leaching of nonylphenol(NP) and bisphenol A (BPA) in the digestive system of the lugworm, _Arenicola marina_ and cod, _Gadus morhua_[82]. They used a biodynamic model to estimate the relative contribution of plastic ingestion to total exposure to chemicals in the ingested plastic. They concluded that MP ingestion by the lugworm or cod is probably not a relevant exposure pathway for either chemical for either animal. Several studies have compared the toxicity of fresh (virgin) MPs with that of \"weathered\" MPs that have been in the environment and have had time to adsorb contaminants from the surrounding water, or with virgin MPs that have been spiked with chemicals. Virgin MPs are assumed to have no attached toxicants, while weathered ones would be expected to have accumulated them from the environment. Intertidal snails (_Littorina littoria_) were exposed to leachates from both virgin and beached pellets [59]. While virgin pellets impaired vigilance and antipredator behavior slightly, beached pellets severely inhibited these behaviors. These results indicate that effects from MP leachates may have serious consequences for animals that rely on chemosensory cues to escape predation.