Do Coffee Makers Release Microplastics?

It’s likely that coffee makers release microplastics. While there hasn’t been a publication confirming this,  it isn’t a stretch to assume that the simple process of exposing plastic to heat, water, and pressure results in the generation of microplastic fragments. As research into microplastic continues, coffee preparation has emerged as a relevant and understudied pathway for microplastic ingestion. The latest research shows that while not all coffee makers release the same amount of microplastics, common coffee makers release measurable microplastics and nanoplastics into one of our favorite drinks. 

Why Coffee Makers Are a Relevant Microplastic Exposure Source

Unless you’re using a French press, making coffee involves heating water to near-boiling temperatures while exposed to plastic surfaces. This heat, combined with the stress and pressure from pumps, filters, and flow restriction, accelerates the degradation of microplastics from plastic coffee markers [1]. As the polymers that comprise plastics weaken under these conditions, microscopic fragments detach and become suspended in the beverage.

Evidence of Microplastics from Single-Use Drip Coffee Bags

The most direct evidence of microplastic release while making coffee comes from single-use plastic drip coffee bags. These bags are designed to hold ground coffee while hot water is poured directly through the synthetic fibers. 

Experiments show that a single plastic coffee bag can release more than 10,000 microplastic particles into one cup of coffee [1]. The particles are primarily composed of polypropylene, polyethylene terephthalate, and rayon, appearing as irregular fragments and fibers [1,2]. The release mechanism closely mirrors the process observed in plastic teabags. As with teabags, the plastic polymers begin to break down quickly when in near-boiling water [2]. 

Plastic Kettles and Heating Elements Used with Coffee Makers

Electric kettles are commonly used to supply hot water for pour-over, French press, and manual espresso preparation. When these electric kettles are made of plastic or plastic heating components, they become a substantial source of microplastic contamination.

Studies report that water boiled in plastic kettles contains between roughly 4 million and 35 million microplastic particles per liter of water. This is a staggering amount. Conversely, if the water isn’t heated, the numbers are significantly lower [2]. Approximately 80 percent of these particles measure less than 5 micrometers, a size range associated with higher biological interaction potential [2]. The dominant driver of this release is thermal loading, which compromises the structural stability of polypropylene linings during repeated boiling cycles [1].

The Role of Water Chemistry in Microplastic Release

Interestingly, scientists have found that the repeated use of plastic kettles can reduce microplastic release over time by a process known as surface passivation. Mineral deposits, primarily calcium carbonate and metal oxides, precipitate on the inside of the kettle and form a protective barrier that reduces further microplastic generation [1].

This effect is strongly influenced by water chemistry. Hard tap water, which contains dissolved minerals, promotes this process and reduces microplastic release by nearly 90 percent compared to boiling deionized water, which lacks the ions necessary for film formation [1]. 

It’s likely that the Plastic Parts of Coffee Makers Release Microplastics

Modern automatic coffee makers and espresso machines contain plastic tubing, seals, pumps, and heating blocks that are repeatedly exposed to hot water and pressure. Despite this, direct experimental data quantifying microplastic release from internal machine components remains limited [3]. 

However, the materials and operating conditions used in these machines closely resemble those shown to release microplastics in kettles and drip systems. Given the repeated heating and water and tear experienced by internal components, it’s absolutely possible that automatic coffee makers contribute to the creation of microplastics, even though precise emission rates have not yet been measured [3].

Contribution from Cups, Lids, and Industrial Processing

Unfortunately, there are other ways that coffee can acquire microplastics beyond the maker, bags, and filters. For example, disposable paper coffee cups are lined with low-density polyethylene, which degrades when exposed to hot liquids and releases millions and millions of nanoplastic particles [1]. Plastic lids and stirrers can also contribute to the creation of microplastics. In addition, microplastics identified in commercially bottled or canned coffee may originate from the abrasion of plastic piping and equipment during industrial filling [4]. 

Microplastics in Your Coffee – What Does It Mean For You? 

Collectively, the scientific evidence shows that coffee makers and related brewing systems can release microplastics through multiple pathways. The strongest quantitative data implicate plastic drip bags, plastic kettles, and disposable cups, while the exact amount contributed by automatic coffee makers remains unknown in the scientific literature [1–3]. Given the frequency of coffee consumption, even modest per-cup contributions may meaningfully affect long-term dietary microplastic exposure.

The Deplasto platform, consisting of a scientifically-backed nutritional supplement, an iOS app for tracking daily microplastic intake, and a portfolio of lifestyle recommendations intended to help you minimize microplastics. Our nutritional supplement is formulated to support your body’s natural detoxification pathways, including oxidative stress management, cellular repair, and antioxidant support. Our microplastic intake app enables you to estimate and track your daily microplastic intake, with each datapoint backed by scientific studies. Our lifestyle recommendations, found in our blogs and in our eBook, have a plethora of actions and advice designed to help you make small changes to minimize microplastics.

Overall, we believe that the best way to eliminate microplastics begins with you and the small changes you make to your daily life. Over time, collectively, we can make a significant difference.

Sources

1. A systematic review of microplastics emissions in kitchens – Understanding the links with diseases in daily life
2. A systematic review and quality assessment of estimated daily intake of microplastics through food
3. Beyond the food on your plate – Investigating sources of microplastic contamination in home kitchens
4. Internal and external microplastic exposure in young adults – A pilot study involving 26 college students in Changsha, China