Foundations
Jun 30, 2024
Microplastics and Health Risks: A Comprehensive Guide
A look at what microplastics are and how they might impact human health.
Plastic has become essential to modern life, used in everything from packaging to clothing to building materials. But as our reliance on plastic has grown, so has a new health threat: microplastics.
What are plastics?
Plastics are synthetic materials made from long chains of repeating molecular units called polymers, often derived from fossil fuels like oil and gas. Synthetic polymers are lightweight, durable, and can be molded into any shape. They are mixed with additives like plasticizers, stabilizers, and pigments to give plastics additional properties like flexibility, hardness, and color. At least 16,000 chemicals are used in plastics production.
These versatile properties, with low production costs and readily available raw materials, have led to an unprecedented rise in plastic use across industries. Plastic production has grown exponentially since its adoption in the 1950s. Global cumulative plastic production is projected to skyrocket from 9.2 billion tons in 2017 to 34 billion tons by 2050.
It is these same properties that make plastics so valuable that they also lead to the problem of microplastics. Plastics don't decompose quickly when exposed to elements like sunlight and water. Instead, they break down into smaller and smaller fragments.
Microplastics are plastic fragments less than 5 mm - about the size of a sesame seed. Even smaller particles, less than one μm, are called nanoplastics. Invisible to the naked eye, these tiny particles can easily spread through the environment and infiltrate cellular and biological barriers.
Human exposure to microplastics
Humans are constantly exposed to microplastics from synthetic clothing, vehicle tires, plastic packaging, and countless other sources that we come into contact with through air, water, and food.
Indoor air can contain up to 14,000 particles of plastics per cubic meter, with synthetic textiles as a significant source. Outdoor air is also contaminated. Road traffic contributes significantly to airborne microplastic pollution from tire and brake wear. Once in the air, these small plastic particles can travel thousands of miles and pollute areas far from their original sources. It's unlikely any area of the earth is free from microplastic contamination. They have now been discovered everywhere, from remote mountaintops to uninhabited islands.
Most of the water we drink contains microplastics. A 2019 study detected microplastics in 83% of global tap water samples. Bottled water likely contains higher levels of microplastics, and one liter of bottled water might contain up to 240,000 plastic particles.
Our food contains microplastics. Plastic packaging is a significant contributor because food items can absorb microplastics from their containers during storage and transportation. Contamination also occurs earlier in the food production cycle. Plants can absorb plastic particles in the soil through their roots, and animals ingest plastic particles in their feed. A 2024 Environmental Pollution study found that 88% of meat, seafood, and plant protein sources contained microplastics.
Some estimates suggest the average American consumes a credit card's worth of plastic per week. Measuring exposure levels is challenging due to the diversity in chemical composition, size, shape, and surface properties of plastics. However, there is no doubt that microplastics consumption is now a universal reality for humans.
What happens to microplastics in our bodies?
The extent of microplastics in the human body remains unclear. Some pass through the digestive system, while others persist.
Microplastics have now been found in nearly every area of the human body tested, including:
Digestive tract: Ingested microplastics have been found throughout the digestive tract, including stool samples.
Lungs: Microplastics have been found in lung tissue samples, likely from inhaling air polluted with plastic particles.
Brain: Scientists recently found plastic particles in brain tissue. Nanoscale plastic particles were found in all regions of the brain examined.
Placenta: Of particular concern is that microplastics have been found in the placentas of pregnant women, raising the possibility of exposures beginning in utero.
Blood: A landmark 2022 study detected microplastics in human blood for the first time, indicating that plastic particles can travel throughout the body to any tissue or organ.
Are microplastics harmful to humans?
While the presence of microplastics in the human body is concerning, the question remains whether microplastics are harmful to humans.
Researchers have proposed a few potential mechanisms to answer this:
1. Physical damage: Due to their small size, microplastics can infiltrate the smallest compartments of the body and potentially irritate delicate tissues. Inhaled microfibers have been shown to persist for decades in lung tissue and are associated with respiratory disease. Microplastic ingestion has been documented to cause intestinal inflammation and changes to the gut microbiome.
2. Leaching toxic chemical additives: Microplastics can leach chemicals that were added during manufacturing, such as phthalates, bisphenol A, and PFAS. Some of these chemicals can mimic hormones in the body disrupting the endocrine system, and most of them have not been thoroughly studied for their impact on human health.
3. Accumulation of environmental toxins: Microplastics may attract and concentrate other pollutants on their surface. Compounds like PCBs, dioxins, and heavy metals all bind to the surface of microplastics and can be carried into the body when ingested.
Microplastics are diverse, encompassing different plastic types, sizes, shapes, and chemical compositions. This makes studying their health effects especially challenging. Most research has focused on the impacts of microplastic exposure in laboratory animals or cell cultures, with few human studies. While far from conclusive, the available evidence raises major concerns.
Cardiovascular health
A groundbreaking study published in 2023 found that individuals with high levels of microplastics in their coronary arteries had a 350% increased risk of heart attack, stroke, or death compared to those with lower levels, even after controlling for other risk factors. The study does not prove causation, but it is the first to directly link microplastics in the human body to a specific disease and raises an important question for further research.
Fertility
Several studies have shown the potential impacts of plastic-related chemicals and microplastics on male and female fertility. In women, preconception exposure to certain phthalates was associated with decreased probability of pregnancy and changes in reproductive hormones. For men, research using animal models found that microplastic exposure can lead to testes and sperm damage, impaired testosterone production, and reduced sperm quality. These findings suggest that microplastics could threaten reproductive health, but further research is needed to understand their true impact.
Neurotoxicity
Current literature suggests that micro- and nanoplastics can induce neurotoxic effects in various species, particularly aquatic organisms. Observed effects include oxidative stress, altered neurotransmitter levels, and behavioral changes. However, significant knowledge gaps remain, and more research is needed to fully characterize the neurotoxic risks of micro- and nanoplastics in humans. Future research should focus on standardizing exposure conditions, using environmentally relevant particles, and studying a broader range of species, including mammals.
Gut microbiome
A 2022 study found that tiny plastic particles can alter the human gut's microorganism balance. Researchers observed that exposure to these microplastics decreased beneficial bacteria and increased potentially harmful ones using a simulated digestive system. This imbalance could lead to health problems, as gut microorganisms are crucial for digestion and immune function. The study suggests that even small amounts of ingested microplastics, similar to what humans might consume daily, could disrupt our gut microbial community. However, more research is needed to understand the long-term health effects and to explore whether gut bacteria might help break down these plastic particles.
Endocrine system
Many studies have looked at how microplastics and nanoplastics could disrupt the body's hormone system, a process known as endocrine disruption. Plastic particles contain chemicals like bisphenols, phthalates, and heavy metals that are known to interfere with hormone production, reception, and function at high enough exposures. Exposure to these chemicals through microplastics depends on the size of the plastic particles, with smaller particles posing a more significant risk due to increased absorption. While direct effects have been documented, most studies have been conducted on animals or in laboratory settings using concentrations that exceed typical environmental levels, limiting our understanding of their impact on human health.
How to reduce microplastic exposure
Our ever-increasing usage of plastics has outpaced our understanding of their safety. Until their long-term impacts are known, it's recommended to minimize exposure.
Here are several practical steps you can take:
Avoid single-use plastics: Use reusable containers and bottles made of glass or stainless steel instead of disposable options like takeaway coffee cups and plastic water bottles.
Filter your drinking water: Use a high-quality water filter that's certified to remove microplastics.
Vacuum and dust regularly: This helps remove microplastics that accumulate in household dust and get into the air.
Improve indoor air quality: Keep windows open when possible to allow fresh air circulation, and use a high-efficiency particulate air (HEPA) filter to remove microplastics from indoor air.
Avoid storing and heating food in plastic: Use glass, stainless steel, or ceramic containers for microwaving and storing foods.
Choose natural fiber clothing: Synthetic fabrics shed microfibers, so opt for cotton, wool, and other natural materials when possible.
Choose plastic-free tea bags: Many tea bags contain plastic which leaches into hot water; opt for loose-leaf tea or plastic-free options.
Key takeaways
Microplastics are everywhere - including your body
Microplastics have infiltrated virtually every aspect of our environment, from the air we breathe to the water we drink and the food we eat. These tiny plastic particles, less than 5mm in size, have been detected in human lungs, brain tissue, and even blood, which indicates that they can make it to any part of the body.
We're still learning about their health impacts
While research is ongoing, studies suggest microplastics may cause physical damage, leach toxic chemicals, and accumulate environmental pollutants in our bodies. Potential health effects include cardiovascular issues, fertility problems, and disruptions to the gut microbiome and endocrine system.
You can reduce your exposure
Take simple steps to minimize microplastic intake. Use reusable containers, filter your drinking water, improve indoor air quality, and choose natural fiber clothing. Small changes in daily habits can decrease your exposure until more is known about their health impact.