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What are the bad chemicals in coffee?

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8 min read

According to a 2025 investigation by the nonprofit Clean Label Project, while coffee is generally safe, traces of various contaminants like glyphosate, phthalates, and mycotoxins can be found in some brands. To make informed choices about your brew, it's essential to understand what are the bad chemicals in coffee and how they can be minimized.

Quick Summary

This guide examines potential harmful chemicals and contaminants that can be present in coffee, from mycotoxins and pesticides found on beans to processing byproducts like acrylamide. It explores the health implications of these compounds and offers practical methods to reduce exposure and ensure a cleaner, healthier cup of coffee.

Key Points

  • Acrylamide forms during roasting: The high-heat roasting process naturally creates small amounts of acrylamide, classified as a probable human carcinogen, but levels in brewed coffee are generally low.

  • Mycotoxins can be present in beans: Molds can produce mycotoxins like Ochratoxin A and Aflatoxin B1 on coffee beans, but proper processing and roasting significantly reduce these levels to generally safe concentrations.

  • Conventional coffee may contain pesticides: Conventionally farmed coffee is heavily treated with pesticides, and residues can sometimes persist, making certified organic options a safer choice.

  • Packaging can introduce chemicals: Plastic-lined pods and canned coffee may contain phthalates, which can leach into the brew and are associated with hormone disruption.

  • Water process is best for decaf: Decaf coffee using the Swiss Water Process avoids chemical solvents like methylene chloride, which are used in some other decaffeination methods.

  • Filtered coffee is safer for cholesterol: Using a paper filter removes diterpenes like cafestol and kahweol, which can raise LDL ('bad') cholesterol, particularly with unfiltered brewing methods.

  • Roast type matters: Lighter roasts retain more beneficial compounds like chlorogenic acids, while darker roasts have lower acrylamide but may contain more PAHs and less antioxidants.

  • Brewing method influences chemical levels: Volatile compounds like furans decrease with cooling, and filtration can reduce certain undesirable compounds, giving consumers control over the final product.

In This Article

Coffee, a beloved beverage worldwide, can harbor various chemicals and contaminants from cultivation to processing. While low levels of these compounds are generally not a concern for most consumers, understanding what they are and how to minimize exposure can benefit overall health. The potential health risks posed by coffee’s harmful chemicals have received considerable media coverage over the years, leading many health-conscious individuals to scrutinize the source and preparation of their daily brew. This article breaks down the primary chemical concerns in coffee and provides actionable strategies for a cleaner, safer cup.

Chemicals Formed During Processing and Roasting

Acrylamide

Acrylamide is a chemical that naturally forms during the high-heat roasting of coffee beans, a process known as the Maillard reaction. This reaction is also responsible for the aroma and browning in many starchy foods, including roasted vegetables and baked goods. Although classified as a probable human carcinogen by the International Agency for Research on Cancer (IARC), the levels found in brewed coffee are generally considered too low to pose a significant health risk for moderate consumers.

  • How it forms: A chemical reaction between sugars and the amino acid asparagine during high-temperature roasting.
  • Levels and Roasting: Acrylamide levels often peak early in the roasting process and then decrease as roasting continues. This can result in medium roasts having slightly higher levels than both light and dark roasts. Instant coffee and roasted grain substitutes tend to contain the highest concentrations.

Furans

Furans are another class of chemical compounds formed during the thermal processing of food, including coffee roasting. Furan is classified as a possible human carcinogen by the IARC based on animal studies. Furan is highly volatile, and a significant portion is lost during the grinding and brewing process. For example, studies have shown that levels of furans can decrease significantly when coffee cools and is stirred.

  • Where it's found: Higher furan concentrations have been detected in espresso and capsule coffees due to their preparation methods, while instant coffee generally has lower levels.
  • Consumer Behavior: Consumer behavior, such as stirring coffee and allowing it to cool before drinking, can significantly reduce furan exposure due to its volatility.

Polycyclic Aromatic Hydrocarbons (PAHs)

Polycyclic Aromatic Hydrocarbons (PAHs) are a group of chemicals that form during the incomplete combustion of organic materials. In coffee, PAHs can form during high-temperature roasting. The concentration of PAHs is often linked to the roasting intensity, with dark roasts sometimes containing higher levels than light roasts.

  • Risk Factors: Some PAHs are known carcinogens, but due to their low water solubility, minimal amounts transfer from roasted beans to the final brewed cup.
  • Reducing Exposure: Opting for lighter roasts and brands with controlled roasting processes can help minimize exposure.

Contaminants Found in the Beans

Pesticides and Herbicides

Conventionally grown coffee is often treated with pesticides and herbicides to protect crops and maximize yield. While most of these chemicals are either destroyed during roasting or do not survive the brewing process, some, like glyphosate, can persist in the beans and end up in your cup. Choosing certified organic coffee is a primary way to avoid pesticide residues.

  • Glyphosate: Traces of this common herbicide have been detected in some coffees, although regulatory bodies and risk assessments typically report minimal levels.
  • Organic Farming: Certified organic farms prohibit the use of synthetic pesticides and herbicides, minimizing the risk of these chemicals appearing in the final product.

Mycotoxins

Mycotoxins are toxic compounds produced by molds that can grow on coffee beans, particularly when they are stored improperly in warm, humid conditions. Two of the most-researched mycotoxins in coffee are Ochratoxin A (OTA) and Aflatoxin B1, both of which are considered potential carcinogens at high levels. The roasting process significantly reduces mycotoxin levels, and regulatory limits ensure that commercially available coffees contain amounts far below health-risk levels.

  • OTA and Aflatoxin: These mycotoxins are prevalent in many food crops but are largely mitigated in coffee through proper processing and roasting.
  • Control Measures: High-quality coffee beans that are wet-processed and stored in temperature-controlled facilities are less likely to contain mycotoxins.

Heavy Metals

Heavy metals like lead, mercury, and arsenic can find their way into coffee beans through the soil in which the plants are grown. The levels of heavy metals can vary depending on the coffee's origin, with some regions naturally having higher soil concentrations than others. A 2025 study by the Clean Label Project found that while heavy metals were detected, the levels were minimal and well below established safety limits.

Contaminants from Packaging and Equipment

Phthalates and Endocrine Disruptors

Phthalates are chemicals often used to make plastics more flexible and are found in many consumer products. They can migrate from packaging materials, like plastic-lined coffee pods or canned coffee, into the brew. Some phthalates are considered endocrine-disrupting chemicals, which can affect hormones. A recent study found the highest levels of phthalates in canned coffee, followed by pods, and the lowest in bags.

Methylene Chloride (in decaf coffee)

Some decaffeination processes, particularly the direct solvent-based method, use methylene chloride. While this is a very effective way to remove caffeine, trace amounts of the chemical can remain in the beans. If you prefer decaf, you can choose brands that use a chemical-free decaffeination process, such as the Swiss Water Process, which uses only water to remove caffeine.

Comparison of Potential Chemical Risks in Coffee

Chemical/Contaminant Origin Health Concern (at high doses) Impact of Roasting/Processing How to Minimize Risk
Acrylamide Formed during high-heat roasting. Probable human carcinogen, neurotoxin. Levels fluctuate; often lower in dark roasts and highest in instant coffee. Opt for darker roasts, choose high-quality arabica beans.
Mycotoxins (OTA, Aflatoxin) Produced by molds on beans due to improper storage. Kidney damage, potential carcinogen. Reduced significantly by proper wet-processing and roasting. Buy certified organic, high-quality, whole-bean coffee.
Pesticides/Herbicides Used in conventional farming. Potential endocrine disruptors, neurotoxic effects. Most are destroyed, but some residues can remain. Choose certified organic coffee.
PAHs Formed during high-temperature roasting. Suspected carcinogens/mutagens. Minimal transfer to brew due to low water solubility. Opt for light to medium roasts; controlled roasting methods.
Furans Formed during high-heat roasting. Possible human carcinogen based on animal studies. Volatile and lost during brewing/cooling. Stir and allow coffee to cool before drinking.
Phthalates Leaching from plastic packaging. Endocrine disruption, reproductive issues. Contamination depends on packaging materials. Use non-plastic brewing methods and avoid pods/cans.

How to Reduce Harmful Chemical Exposure in Your Coffee

For the health-conscious consumer, several strategies can help reduce the intake of potentially harmful chemicals in your daily coffee ritual:

  1. Choose Certified Organic Beans: Certified organic coffee beans are grown without the use of synthetic pesticides and herbicides, directly addressing one source of contamination. Some organic farms may still be exposed to runoff from conventional farms, but the overall risk is significantly lower.
  2. Opt for High-Quality, Whole-Bean Coffee: High-quality beans are typically subjected to better processing and storage practices, reducing the risk of mold growth and subsequent mycotoxin formation. Grinding whole beans just before brewing also ensures maximum freshness and minimizes chemical degradation.
  3. Use Filtered Water: The water used to brew your coffee can contain unwanted substances like chlorine, fluoride, and other contaminants. A high-quality water filtration system can remove these, improving both the safety and taste of your coffee.
  4. Use a Paper Filter: While unfiltered brewing methods like a French press or Moka pot produce a richer flavor, they allow diterpenes like cafestol and kahweol to pass into the brew. Paper filters can trap these compounds, which are known to increase cholesterol, and may also reduce trace amounts of other chemicals.
  5. Choose Darker Roasts: Darker roasts generally have lower levels of acrylamide and potentially fewer mycotoxins due to the longer roasting time. The trade-off is that very dark roasts can have higher levels of some PAHs. A balanced approach might involve a dark roast or very light roast.
  6. Avoid Plastic Components: Hot water can cause plastics to leach chemicals like phthalates into your brew. Avoid using coffee pods or brewing equipment with plastic parts that come into contact with hot water. Stainless steel, glass, or ceramic brewers are safer alternatives.
  7. Be Mindful of Decaf Choice: For decaf drinkers, choosing brands that explicitly state they use a water process, like the Swiss Water Process, is key to avoiding residual chemical solvents like methylene chloride.

Conclusion

While coffee offers numerous potential health benefits, the presence of various chemicals, from agricultural residues to roasting byproducts, raises valid questions for health-conscious consumers. The risks associated with these chemicals at the levels found in most store-bought coffee are generally considered low for moderate drinkers. However, by being a discerning consumer and making informed choices about the type of beans, roasting process, and brewing methods used, it is possible to significantly reduce potential chemical exposure.

From opting for certified organic, high-quality whole beans to using filtered water and paper filters, several practical steps can be taken to ensure your cup of coffee is as clean and healthy as possible. Ultimately, staying informed and prioritizing transparency from growers and roasters empowers you to enjoy your coffee ritual with greater peace of mind.

References

Frequently Asked Questions

Acrylamide is a chemical compound that naturally forms when coffee beans are roasted at high temperatures. It is a byproduct of the Maillard reaction, which gives roasted coffee its characteristic color and flavor. The amount of acrylamide is typically higher in medium roasts compared to light and dark roasts, and highest in instant coffee.

Yes, conventionally grown coffee is often treated with pesticides and herbicides, and residues can remain on the beans and potentially transfer into your brew. Choosing certified organic coffee beans is the best way to avoid these chemicals, as organic farming prohibits their use.

Mycotoxins are toxins produced by molds that can grow on coffee beans, especially when stored in humid conditions. While mycotoxins like Ochratoxin A are a concern, proper processing, and roasting significantly reduce their levels. The amounts found in commercial coffee are typically well below regulatory safety limits.

Yes, if your brewing equipment contains plastic parts that come into contact with hot water, there is a risk of chemicals like phthalates leaching into your coffee. This is particularly true for single-serve plastic pods and some coffee makers with plastic reservoirs. Using stainless steel, glass, or ceramic alternatives is a safer option.

For those concerned about cholesterol, filtered coffee is considered healthier. Paper filters trap diterpenes, compounds that can raise LDL ('bad') cholesterol, which are more prevalent in unfiltered brews like French press or Turkish coffee.

Some methods of decaffeination use chemical solvents, such as methylene chloride, which can leave trace residues in the beans. To avoid these, choose brands that use chemical-free decaffeination processes, such as the Swiss Water Process, which uses only water.

To reduce chemical exposure, you can choose certified organic coffee beans, use filtered water for brewing, opt for paper filters or non-plastic brewing equipment, and select dark roasts, which typically have lower acrylamide levels.

References

  1. 1
    Caffeinated coffees are mostly free of toxins, with a few exceptions
  2. 2
    Toxins in Coffee: What Pesticides and Herbicides Could Be In Your Morning Cup?
  3. 3
    Acrylamide in Coffee: Is it harmful, and does it cause cancer?
  4. 4
    Acrylamide in Coffee: Understanding the Facts
  5. 5
    The Dirty Side of Coffee - and how to choose a healthier cup
  6. 6
    Toxins in Coffee: 7 Sources of Harmful Chemicals in Your Morning Brew
  7. 7
    What's the healthiest way to brew coffee?

Related Topics:

#coffee #Healthy Coffee #coffee health #pesticides #Mycotoxins #acrylamide #Food chemicals #PAHs

Medical Disclaimer

This content is for informational purposes only and should not replace professional medical advice.