Dangers & Health Effects of Microplastics Exposure in Humans

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Microplastics, the tiny plastic particles polluting our environment, are increasingly being linked to potential adverse health effects in humans. Here’s what you need to know about this emerging public health issue.

Key Facts:

  • Microplastics are plastic particles smaller than 5 mm that are widespread pollutants in the environment. They come from the breakdown of larger plastic products or microbeads in consumer products.
  • Humans are exposed to microplastics through ingestion, inhalation, and skin contact. Food and drinking water are major sources of exposure.
  • Laboratory studies show microplastics can cause inflammation, oxidative stress, endocrine disruption, reproductive issues, and other problems in human cells and animals.
  • More research is urgently needed on microplastic toxicity mechanisms and actual health impacts in humans, as exposure is ubiquitous.

Source: Yonsei Med J 2023

What Are Microplastics?

Microplastics are tiny plastic fragments or particles less than 5 mm in size that have become pollutants of serious concern.

They are found in aquatic environments worldwide, from the oceans to inland lakes and rivers.

Microplastics also pollute land environments and the air.

There are two main types of microplastics:

  • Primary microplastics are purposefully manufactured small plastic particles. A common example is the microbeads previously used in some cosmetic products and consumer goods.
  • Secondary microplastics form when larger plastic products break down into smaller fragments through processes like UV radiation and mechanical abrasion.

Microplastics come in various shapes (spheres, fibers, fragments, etc.) and consist of many different plastic polymer types, including polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyester.

Microplastics are highly persistent and accumulate in the environment because they do not biodegrade. Their small size also makes them nearly impossible to remove once released.

Microplastics Sources & Exposure Routes in Humans

Microplastics have become ubiquitous worldwide, increasingly found even in remote regions. Human exposure sources include:

  • Food and drinking water – Major route of exposure is ingestion through water and food contaminated with microplastics. Seafood and sea salt have been found to contain microplastics.
  • Air – Microplastic fibers and particles are in the air, leading to inhalation exposure. Indoor air has higher levels than outdoor air.
  • Consumer products – Microbeads previously used in cosmetics and some cleaning/personal care products can directly release microplastics. Textiles made of synthetic materials are also a source.
  • Dust – Indoor dust contains microplastic fibers shed from textiles and fibers in upholstery.
  • Packaging – Plastic packaging materials degrade over time into microparticles that contaminate food.

Average daily human exposure to microplastics is estimated to range from tens of thousands to over a million particles, or several milligrams in mass, though estimates vary widely.

The upper end shows the potential for extremely high exposure over a lifetime.

Potential Health Effects & Dangers of Microplastic Exposure

The ubiquity of microplastic exposure raises concerns over potential health hazards, though significant knowledge gaps remain. Some key points about their health risks:

  • Physical effects: Ingested microplastics could cause physical damage to organs as they pass through the gastrointestinal tract. Meanwhile, inhaled particles may irritate airways.
  • Chemical toxicity: Chemical additives in plastics, such as plasticizers, can leach from microplastics and accumulate in body tissues. Many additives are endocrine disruptors.
  • Adsorption: Microplastics tend to adsorb other toxic environmental contaminants like heavy metals and organic pollutants that can also be transferred to the body.
  • Inflammation: Exposure to microplastics is linked to inflammatory responses, likely caused by both physical irritation and chemical toxicity. Chronic inflammation can lead to a range of diseases.
  • Oxidative stress: Cell studies show microplastics can cause excess reactive oxygen species production and oxidative stress, which damages DNA, proteins, and cell membranes and is tied to cancer, aging, and other diseases.
  • Endocrine effects: Through interactions and interference with the endocrine system, microplastics may alter hormone levels and cause reproductive, developmental, and metabolic disorders.
  • Microbiome: Gut microbes may be impacted by microplastics passing through the digestive system, leading to an imbalance between beneficial and harmful bacteria.
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Given their small size, microplastics can cross cell membranes and bioaccumulate inside cells and tissues.

This raises additional toxicological concerns not seen with larger plastic debris.

Unclear Human Health Effects of Microplastics Exposure

Despite laboratory evidence showing microplastics can damage human cells and cause problems in animals, substantial research is still needed to firmly establish the human health impacts.

Major knowledge gaps include:

  • Dose-response data: Lack of toxicity studies exposing cells or lab animals to realistic microplastic doses makes human health risks difficult to quantify.
  • Impact of size/shape: Toxicity likely depends heavily on microplastic size, surface properties, and shape, but this requires further study.
  • Chronic exposures: Long-term low-dose exposures that mimic real world scenarios need to be tested in animal models to reveal impacts over a lifetime.
  • Epidemiology studies: There is almost no epidemiological data associating microplastic exposures with incidence of human diseases or conditions. These large-scale population studies are critically needed.
  • Mode of action: Mechanistic understanding is incomplete in terms of how microplastics interact with cells/tissues and lead to specific health effects like oxidative stress, endocrine disruption, etc.

Without filling these major research gaps, estimating the human health risks posed by ubiquitous microplastic pollution remains speculative.

Regulation and Policies to Reduce Microplastics Exposure

Many countries have policies in place to reduce primary microplastic use and pollution in an effort to curb human exposure:

  • Bans on microbeads in cosmetics/consumer goods – The U.S., Canada, U.K., Taiwan, and others have banned the use of plastic microbeads as exfoliants and for other uses.
  • Restrictions on single-use plastics – Items like plastic bags, straws, and cutlery are limited in the E.U. and some other regions to reduce microplastic pollution.
  • Improved plastic waste management – Strategies like plastic recycling targets and extended producer responsibility laws aim to prevent plastic debris from degrading into secondary microplastics.
  • Wastewater treatment upgrades – Advanced filtration to remove microplastic particles from effluent before discharge into water bodies.

Public education campaigns encouraging consumer behavior to reduce plastic use and proper recycling and disposal of plastics are also an important piece of the strategy.

While regulatory measures can help restrict microplastic pollution at the source, there are also technical countermeasures that could reduce exposure:

  • Air filtration systems – High efficiency particulate air (HEPA) filters capture airborne microplastics in buildings and cars.
  • Water filtration – Ultrafiltration and reverse osmosis membranes in treatment systems can remove microplastics from drinking water.
  • Wastewater treatment – Advanced tertiary treatment using membrane bioreactors is much more effective at removing microplastics than standard secondary treatment.

Future Research Directions

The study of human exposures and health impacts related to microplastics is a new and rapidly evolving field. Some key future research priorities include:

  • Exposure assessment – More data is needed on microplastic concentrations in air, food/water, consumer products, and human tissues. Exposure levels across world populations should then be quantified.
  • Toxicology – Chronic animal studies at realistic doses are critical for understanding long-term impacts. In vitro toxicity studies must also consider different sizes, shapes, and polymer types.
  • Epidemiology – Rigorously establish links between microplastic exposures and human diseases/conditions, focusing first on strongly exposed populations.
  • Risk assessment – Combine exposure, toxicology, and epidemiology data to estimate potential health risks for the general population and vulnerable groups in different exposure scenarios.
  • Mitigation – Develop practical and cost-effective technologies to remove microplastics from wastewater, drinking water, air, and food items.

Tackling the problem of ubiquitous microplastic pollution will require cross-disciplinary collaboration between polymer chemists, environmental engineers, toxicologists, epidemiologists, and public health experts.

Additional research funding priorities must be directed toward this emerging environmental health threat.

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