probably isn’t toxic at all and will degrade to simple carbon, nitrogen, phosphorus, and sulfur. But we don’t really know for sure, do we? A recent study by de Souza
(Environmental Science and Technology 53: 6044) found an increase in arbuscular mycorrhizal fungi, a key symbiont group that associates with plant roots. If generally true, this could affect nutrient cycling, because these symbionts transport key nutrients, including phosphorus, to their plant hosts. Feedbacks to the Earth system can be expected. Microplastic is composed of fossil carbon, which might indirectly affect rates of net primary production and carbon storage in soils and alter the fluxes of greenhouse gases. Te direction, magnitude, and balance of these effects should be a focus of future research.
Microplastics and
human health Recent evidence indicates that
humans constantly inhale and ingest microplastics; however, whether these contaminants pose a substantial risk to human health is far from understood. Despite a lack of crucial data on the exposure and hazards of microplastics to our health, Vethaak and Legler (Science 371[6530]) show parallels that can be drawn with particulate air pollution, whereby small particles (< 2.5 μm), such as those from diesel exhaust, are capable of crossing cell membranes and triggering oxidative stress and inflammation, and have been linked with increased risk of death from cardiovascular and respiratory diseases or lung cancer. Tis parallel provides ample incentive to gather more information on the potential risk of microplastic particles and their paper mostly points out how little is currently known with regards to microplastics and human health.
Disease transmission Tere is mounting evidence that
microplastic surfaces in aquatic environments host microorganisms that are resistant to antibiotics. Tis suggests that plastic pollution could have ramifications on disease transmission and treatment in addition
to environmental consequences and human exposure to contaminated air, water, and food (Science; vol. 369, no.6509). Bacterial biofilms found on microplastics in aquatic ecosystems have been shown to include bacteria with antibiotic-resistant genes. Tese resistant bacteria likely originate in human and animal populations treated with antibiotics and then travel downstream through wastewater into riverine and marine ecosystems. Te increasing surface area provided by waste plastics, such as polyethylene, may enable higher rates of biofilm growth, including those containing antibiotic- resistant genes. Te possibility that plastic pollution can facilitate resistance to antibiotics has critical implications for the spread of disease and the management and regulation of antibiotic resistance in the environment.
Fungi to the rescue! We all know fungi are really amazing.
Although we don’t (yet) know of any that are autotrophic (though there are hints of radioautotrophy coming from nuclear reactor studies), they are amazingly diverse as heterotrophs, seemingly able to utilize just about any organic compounds in the environment as a source of energy and nutrition. What about plastics? It turns out that promising research is showing some fungi can even break down plastics. In 2011, Yale University students made headlines with the discovery of a fungus in Ecuador, called Pestalotiopsis microspora, that has the ability to digest and break down polyurethane plastic. Even more exciting, the fungus seems to be able to thrive in anaerobic situations—which might even make it effective buried in landfills. Researchers at Utrecht University have shown strains of the ubiquitous mushroom species Pleurotus ostreatus (Oyster) and Schizophyllum commune (Split Gill) could fully degrade small pieces of plastic while growing in culture. And in 2017, Sehroon Khan and other researchers at the World Agroforestry Centre in Kunming, China discovered another biodegrading fungus (found in a landfill in Islamabad, Pakistan), Aspergillus tubingensis, which can grown on and degrade polyester polyurethane. You may not recognize the name, but you know the plastic—it
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