Materials that are not safe for food contact include galvanized metal, unlined copper, lead-glazed ceramics, and non-food-grade plastics. These surfaces can leach harmful chemicals into food, especially acidic foods like tomato sauce, citrus juice, or vinegar. If you encountered this question on a food safety exam, the most common correct answer is galvanized metal, but several other materials also fail to meet food contact standards.
Galvanized Metal
Galvanized metal is one of the most frequently cited unsafe food contact surfaces in food safety training. Galvanized means the iron or steel has been coated with zinc to prevent rusting. While zinc is a mineral your body needs in small amounts, it becomes toxic when consumed in large quantities. The problem is that acidic or high-moisture foods cause zinc to leach from the coating and convert into zinc salts, which your body absorbs readily. Symptoms of zinc poisoning include vomiting, nausea, fatigue, and stomach pain. Most documented cases of zinc poisoning from food trace back to storage in galvanized containers.
Food codes specifically prohibit galvanized metal for utensils or food contact surfaces that will touch acidic food. This is why you won’t see galvanized buckets, bins, or trays approved for food prep in commercial kitchens, even though they’re common in gardening and construction.
Unlined Copper
Copper cookware is prized for its heat conductivity, but bare copper is not safe for most foods. The FDA Food Code recommends that any food or beverage with a pH below 6.0 should not contact copper or copper alloy surfaces due to the high risk of copper leaching. That threshold covers nearly everything you’d cook or store: fruits, vegetables, dairy, meat marinades, wine, coffee, and any sauce with tomato or vinegar.
Research on copper leaching found a direct relationship between the amount of copper transferred to food, the acidity of that food, and the temperature. Hotter, more acidic foods pull more copper from the surface. This is why safe copper cookware is lined with tin or stainless steel, creating a barrier between the copper and your food. If that lining wears through, the pan is no longer safe for acidic cooking.
Lead-Glazed Ceramics and Pottery
Certain ceramic glazes contain lead, which can leach into food and cause lead poisoning over time. The FDA has flagged several specific types of ceramicware as higher risk: handmade pottery with a crude or irregular shape, antique pieces, anything purchased from flea markets or street vendors, and brightly decorated items in orange, red, or yellow (lead is often added to these pigments to boost their intensity).
Some decorative pottery is stamped on the bottom with warnings like “Not for Food Use — May Poison Food.” These items should never be used for cooking, serving, or storing food or drinks. The FDA has also found that some traditional pottery labeled “lead free” actually contains lead levels comparable to known lead-glazed pieces, so the label alone isn’t always reliable. If you can’t confirm the pottery comes from a manufacturer that tests for lead, it’s safer to use it only for decoration.
Non-Food-Grade Plastics
Not all plastic is created equal. Food-grade plastics must meet specific FDA authorization requirements, meaning every chemical component that could migrate into food has to be approved through recognized safety pathways. Non-food-grade plastics, like repurposed paint buckets or industrial containers, often contain additives called phthalates that make the plastic more flexible and transparent. These chemicals can migrate from the container into food, particularly liquids, and act as endocrine disruptors in the body.
In 2022, the FDA revoked food contact authorization for 25 phthalate-related substances, narrowing the approved list to just nine phthalates for food contact use. This means many plastics that were once technically permissible no longer are. The practical takeaway: only use containers specifically manufactured and labeled for food storage. Hardware store buckets, garbage bins, and repurposed chemical containers are not safe food contact surfaces, regardless of how well you clean them.
Damaged Nonstick Coatings
Nonstick cookware with an intact coating is generally considered safe for food contact. Once that coating is scratched or flaking, the situation changes. Research from the Global Centre for Environmental Remediation found that a single surface scratch on a nonstick coating can release more than 9,000 micro- and nanoparticles. Over the course of cooking a meal, a damaged pan could release as many as 2.3 million tiny plastic particles.
These particles may contain traces of PFAS, a group of chemicals sometimes called “forever chemicals” because they don’t break down easily in the body or the environment. Exposure to certain PFAS has been linked to liver disease, chronic kidney disease, high blood pressure, and some cancers. Nonstick cookware made before 2013 was manufactured with PFOA, a specific PFAS compound linked to kidney and testicular cancers in people with high exposure levels. If your nonstick pans show visible scratches, chips, or peeling, they’re no longer a safe food contact surface.
Worn or Porous Wood
Wood cutting boards are a topic of ongoing debate in food safety, but the research leans in one direction. A study comparing wood and plastic cutting boards found that wood surfaces developed cracks wide enough to trap bacteria after repeated use. When researchers inoculated both surfaces with E. coli and then washed them using standard food service procedures, plastic surfaces came out consistently cleaner. After washing and sanitizing, bacterial colonies were still observed on wood surfaces but never on plastic ones.
Wood boards that had been hand-washed five times before testing performed even worse, suggesting that the wear from repeated cleaning opens up the grain and creates more hiding spots for bacteria. Wood absorbs moisture, and bacteria travel with it into the material where sanitizers can’t reach. This doesn’t mean you need to throw out a well-maintained home cutting board, but in commercial food service settings, heavily worn wood surfaces are considered less desirable from a food safety perspective. NSF standards for commercial food equipment also prohibit lead as an intentional ingredient in food contact materials, with narrow exceptions for certain brass and bronze components.
How Materials Get Approved for Food Contact
The FDA doesn’t publish a simple list of banned materials. Instead, every substance that could reasonably migrate from a food contact surface into food must be authorized through one of several pathways: it must be listed as an approved indirect food additive, recognized as generally safe, covered by a prior approval, or cleared through a formal notification process. If a material doesn’t fit any of those categories, it’s not legal for food contact until the manufacturer submits new safety data and receives authorization.
This system means the burden falls on manufacturers to prove their materials are safe, not on regulators to test every product on the market. For consumers, the simplest guide is to use cookware, containers, and prep surfaces that are explicitly marketed for food use by established manufacturers. Repurposed, decorative, or industrial materials carry real chemical risks that washing alone cannot eliminate.