A California study shows that the most commonly produced plastics that are littered in the environment are also the ones that absorb the most chemicals, a finding that poses a greater risk for marine animals and those that eat them.
The absorption ability of these plastics continued for longer periods of time than previously thought. Chelsea Rochman, a doctoral student at University of California, Davis’ School of Veterinary Medicine, conducted the study for 12 months at five locations in San Diego Bay, the school reports. The study, whose results are published in the journal, Environmental Science & Technology, is the first controlled, long-term field experiment measuring the absorption of contaminants by the five most common plastics.
Those plastics are: 1) polyethylene terephthalate (PET), commonly used in water bottles; 2) high-density polyethylene (HDPE), used in detergent bottles; 3) polyvinyl chloride (PVC), commonly used in clear food packaging; 4) low-density polyethylene (LDPE), found in plastic shopping bags; and 5) polypropylene (PP), commonly used in yogurt containers and bottle caps.
The university explains how Rochman did her research:
Rochman and her colleagues deployed pellets of each plastic type in mesh bags tied to a dock at each study site. They retrieved them periodically to measure the plastics’ absorption of persistent organic pollutants.
“Consistently in our study, we found polyethylene [HDPE and LDPE] and polypropylene [PP] absorbed much greater concentrations of contaminants than PET or PVC, and those are the most commonly mass produced and consumed plastics,” says Rochman. “They are also the most commonly recovered as marine debris.”
The plastics with the highest absorption rates are also the most common. For example, HDPE, LDPE, and PP accounted for 62% of all plastics produced around the world in 2007, Rochman’s study found. PVC and PET made up 19% and 7%, respectfully, in the world. It was noted that while PVC did not take up proportionately as many pollutants as the other plastics, vinyl chloride is considered a carcinogen and toxic.
The researchers also were surprised at how long the plastics absorbed contaminates while in the environment, reports Mother Jones. They expected the plastics to absorb pollutants for several months. Instead, they were surprised to find that it would take 44 months for HDPE to stop absorbing pollutants.
“It surprised us that even after a year, some plastics would continue to take up contaminants,” Rochman says. “As the plastic continues to degrade, it’s potentially getting more and more hazardous to organisms as they absorb more and more contaminants.”
Source: “Plastics and chemicals they absorb pose double threat to marine life,” UC Davis News & Information, 1/28/13
Source: “Plastics Suck Up Other Toxins: Double Whammy for Marine Life, Gross for Seafood,” Mother Jones, 1/18/13
Image by Nigel Mykura.
Dale McGeehon has been a journalist and editor for more than 25 years, covering chemical regulation and testing for Pesticides and Toxic Chemical News and innovations in material sciences for the National Technology Transfer Center. His writing credits include Omni and College Park magazines and The New York Times.