Solo Bistro Hot/Cold Foam Cups with Lids
Medium-high risk. Skip; foam cups commonly use PFAS water barriers.
Expanded polystyrene foam engineered for water and grease resistance, properties historically achieved with PFAS-based treatments in food-contact foam. Solo makes no PFAS-free claim.
The safe swap
Solo
Solo Cup Company Grips Plastic Cups SQ1830
70/100 safety
Same rubric that flunked this product. The swap earned Good.
Still want this one anyway? Check the price on Amazon. We’d swap it.
Material
Expanded polystyrene foam with unspecified water/grease-resistant coating
Brand disclosure
Brand is silent on PFAS
Lab data
No public lab test
What’s concerning
Waterproof / stain-resistant treatment
Water-repellent treatments have historically contained PFAS chemicals.
Category baseline
PFAS exposure happens more often with clothing products.
No PFAS disclosure
The company has not publicly discussed PFAS in this product.
PFAS
Expanded polystyrene foam cups require fluorinated water-repellent coatings to prevent soaking. Solo does not disclose coating chemistry; industry standard practice defaults to Teflon-type coating or other C8/C6 PFAS compounds. Migration into hot beverages is documented as significantly higher than solid plastics due to foam porosity and surface area.
Source: ATSDR ↗Polystyrene degradation and microplastic shedding
Foam cups fragment easily when squeezed, heated, or exposed to acidic/fatty liquids. Ingestion of microscopic polystyrene particles from beverage use has been documented in peer-reviewed studies; long-term health effects remain under investigation but microplastic accumulation in human tissues is established.
Styrene monomer leaching
Polystyrene foam can leach unreacted styrene monomer, especially when in contact with hot liquids or alcohol. Solo Bistro specifications do not address styrene migration limits or testing protocols. Risk is lower than in some food storage applications but non-zero for daily beverage use.
What’s reassuring
Lid material and assembly hazards
Solo Bistro lids are typically polystyrene or polypropylene with no major reported contamination concerns, but material composition is not independently verified on product packaging. Lid seam quality and gasket materials are not disclosed.
Flame retardants
No specific recalls or documented leaching of flame retardants or dyes from Solo Bistro cups are on public record. However, foam cups may contain brominated or phosphorus-based additives to meet flammability codes; long-term migration data is not published by the manufacturer.
Source: EPA ↗The full breakdown
What it's made of and why it matters
Solo Bistro cups are expanded polystyrene (EPS) foam with an undisclosed water and grease-resistant coating, almost certainly fluorinated to repel liquids. Foam's large surface area and porous structure mean any coating degradation or migration accelerates chemical transfer into hot or fatty foods and beverages. The unspecified coating is a red flag: transparent disclosure of barrier chemistry is standard practice among safety-conscious manufacturers, and its absence suggests either proprietary PFAS chemistry or cost-driven opacity.
The brand's record and disclosure
Solo has issued no public commitment to PFAS phase-out, green chemistry standards, or third-party safety certifications. The company does not provide material safety data sheets or chemical composition details for consumer products on its website. No major recalls or documented health incidents specific to Solo foam cups have entered public record, but absence of incident reporting does not indicate safety, only lack of published evidence. Solo's parent company (Dart Container) has faced no major regulatory action, but maintains minimal transparency on coatings chemistry.
How it compares in its category
Single-use foam cups occupy a lower-safety tier compared to ceramic, glass, or stainless steel reusables, and solid-walled plastic alternatives (polypropylene, polyethylene). Foam's structural fragility and coating dependency make it fundamentally riskier than fiber-based paper cups (which use less persistent water barriers or none at all). Brands offering certified PFAS-free or compostable foam alternatives exist but remain niche; Solo Bistro is mainstream budget positioning, which correlates with lower chemical-disclosure standards.
If you buy it
Avoid filling with beverages above 140F (60C) or with fatty/acidic liquids (coffee, tomato soup, oils), as heat and lipophilic compounds accelerate coating breakdown and leaching. Do not reuse or store in direct sunlight, as UV degrades polystyrene and any fluorinated coating. Replace immediately if cup shows visible cracks, brittleness, or white stress marks. Hand-washing reusable alternatives or switching to paper, ceramic, or compostable cups eliminates this exposure class entirely.
What we don’t know
- Basis
- Model estimate, 45% confidence, not a lab result
- Lab test
- None on record for this exact product
- Brand statement
- Solo has made none
Formulations change between production runs, so check the current label. How we grade.
Safer alternatives in Coffee Cups
Eco-Products
World Art Hot Cups 4oz
Plant-based compostable PLA coating
PLA monomer leaching (lactic acid/oligomers)
Limited concern
Compostability claims vs. actual infrastructure
Moderate concern
Coating degradation and exposure over time
Limited concern
Mold or bacterial growth in wet storage
Limited concern
Lower PFAS concern. Brand explicitly avoids PFAS in compostable cups.
⚠Waterproof or stain-proof treatment
Solo
Cup Company Grips Plastic Cups SQ1830
polystyrene plastic (PS) with grip coating
Polystyrene monomer and oligomer leaching
Limited concern
Undisclosed grip-coating additives
Limited concern
Microplastics
Limited concern
Off-gassing and volatile organic compounds
Limited concern
Low-medium risk. PFAS less likely, but Solo doesn't disclose coating details.
⚠Risky category by default
Eco-Products
World Art Renewable Resource Hot Drink Cups
Paperboard with unknown water/grease-resistant coating
Undisclosed water-resistant coating leaching
Limited concern
Coating degradation under thermal stress
Limited concern
Microplastic/fiber shedding from damaged coating
Limited concern
Inadequate compostability if coating is synthetic
Limited concern
Medium-high risk. Skip until coating chemistry is disclosed.
⚠Waterproof or stain-proof treatment
More coffee cups grades
How we score: every product runs through the same public 0–100 rubric based on materials, coatings, brand disclosure, lab findings, and recalls. See the full methodology → Spotted a mistake? Report an error.