Impact of Microplastic on Health
Impact of microplastics on wildlife
There are several ways in which plastics can interact or influence wildlife. In the case of microplastics (particles smaller than 4.75 millimeter in diameter), the key concern is ingestion.
Ingestion of microplastics have been shown to occur for many organisms. This can occur through several mechanisms, ranging from uptake by filter-feeders, swallowing from surrounding water, or consumption of organisms that have previously ingested microplastics. There a number of potential effects of microplastics at different biological levels, which range from sub-cellular to ecosystems, but most research has focused on impacts in individual adult organisms.
Microplastic ingestion rarely causes mortality in any organisms. As such, ‘lethal concentration’ (LC) values which are often measured and reported for contaminants do not exist. There are a few exceptions: common goby exposure to polyethylene and pyrene; Asian green mussels exposed to polyvinylchloride (PVC); and Daphnia magna neonates exposed to polyethylene.
In such studies, however, concentrations and exposure to microplastics far exceeded levels which would be encountered in the natural environment (even a highly contaminated one). There is increasing evidence that microplastic ingestion can affect the consumption of prey, leading to energy depletion, inhibited growth and fertility impacts. When organisms ingest microplastics, it can take up space in the gut and digestive system, leading to reductions in feeding signals. This feeling of fullness can reduce dietary intake. Evidence of impacts of reduced food consumption include:
slower metabolic rate and survival in Asian green mussels
reduced reproducibility and survival in copepods
reduced growth and development of Daphnia
reduced growth and development of langoustine
reduced energy stores in shore crabs and lugworms
Many organisms do not exhibit changes in feeding after microplastic ingestion. A number of organisms, including suspension-feeders (for example, oyster larvae, urchin larvae, European flat oysters, Pacific oysters) and detritivorous (for example, isopods, amphipods) invertebrates show no impact of microplastics. Overall, however, it’s likely that for some organisms, the presence of microplastic particles in the gut (where food should be) can have negative biological impacts.
Impact of microplastics on humans
There is, currently, very little evidence of the impact that microplastics can have on humans. For human health, it is the smallest particles – micro- and nano-particles which are small enough to be ingested – that are of greatest concern. There are several ways by which plastic particles can be ingested: orally through water, consumption of marine products which contain microplastics, through the skin via cosmetics (identified as highly unlikely but possible), or inhalation of particles in the air.
It is possible for microplastics to be passed up to higher levels in the food chain. This can occur when a species consumes organisms of a lower level in the food chain which has microplastics in the gut or tissue. The presence of microplastics at higher levels of the food chain (in fish) has been documented.
One factor which possibly limits the dietary uptake for humans is that microplastics in fish tend to be present in the gut and digestive tract — parts of the fish not typically eaten. The presence of microplastics in fish beyond the gastrointestinal tract (e.g. in tissue) remains to be studied in detail. Micro- and nanoplastics in bivalves (mussels and oysters) cultured for human consumption have also been identified. However, neither human exposure nor potential risk have been identified or quantified.
Plastic fibres have also been detected in other food items; for example, honey, beer and table salt. But the authors suggested negligible health risks as a result of this exposure. Levels of microplastic ingestion are currently unknown. Even less is known about how such particles interact in the body. It may be the case that microplastics simply pass straight through the gastrointestinal tract without impact or interaction. A study of North Sea fish, for example, revealed that 80 percent of fish with detected microplastics contained only one particle — this suggests that following ingestion, plastic does not persist for long periods of time. Concentrations in mussels, in contrast, can be significantly higher.
What could cause concern about the impact of microplastics?
Three possible toxic effects of plastic particle have been suggested: the plastic particles themselves, the release of persistent organic pollutant adsorbed to the plastics, and leaching of plastic additives.
There has been no evidence of harmful effects to date – however, the precautionary principle would indicate that this is not evidence against taking exposure seriously.
Since microplastics are hydrophobic (insoluble), and are have a high surface area-to-volume ratio, they can sorb environmental contaminants. If there was significant accumulation of environmental contaminants, there is the possibility that these concentrations could ‘biomagnify’ up the food chain to higher levels. Biomagnification of PCBs varies by organism and environmental conditions; multiple studies have shown no evidence of uptake by the organisms of PCBs despite ingestion whilst some mussels, for example, have shown capability to transfer some compounds into their digestive glands.
To date, there has been no clear evidence of the accumulation of persistent organic pollutants or leached plastic additives in humans. Continued research in this area is important to better understand the role of plastic within broader ecosystems and risk to human health. https://www.naraloca.com is a recycled plastic specialist that promotes the use of recycled PET flakes, recycled PET chips, recycled PP & HDPE granules to various plastic and polyester manufacturers. Plastic recycling reduce the amount of microplastics that enter the ecosystem.