Close to 400 million tons of plastic were manufactured globally during year 2018 with annual growth rates approaching 10%, and over 6 gigatons produced in total since 1950. Plastics eventually undergo fragmentation as a typical first step in their decay, and this enables their widespread distribution by air and water currents. Animals easily internalize microplastics and nanoplastics through ingestion and inhalation, accompanied by risks of bioaccumulation. Biodegradable plastics placed into landfills generate methane and carbon dioxide which cycles through the atmosphere unless captured. A major review of the scientific evidence as of year 2019 did not identify major consequences for human society at current levels, but does foresee substantial risks emerging within the next century. A 2019 study indicated that degradation of plastics through sun exposure, releases both carbon dioxide and other greenhouse gases. Bioplastics with a more natural and rapid carbon cycle have been developed as an alternative to other petroleum-based single-use plastics.