Stainless steel is a popular material in many applications such as kitchenware, medical equipment, architecture, automotive parts, and more. This is because stainless steel provides excellent corrosion resistance, durability, aesthetics, cleanability, and hygienic properties. However, not all stainless steel is created equal when it comes to toxicity. Some types of stainless steel may release harmful substances, especially when exposed to high heat such as cooking. So what kinds of stainless steel are considered non-toxic?
What Makes Stainless Steel Toxic?
Stainless steel derives its corrosion resistance, and ability to be sterilized without deforming, from the presence of chromium. Stainless steel must contain at least 10.5% chromium content by mass in order to form a protective chromium oxide layer on the surface when exposed to oxygen. This oxide layer prevents rust and corrosion.
However, some stainless steel alloys also contain metals like nickel and manganese to enhance certain properties. Nickel improves corrosion resistance, ductility, and strength. Manganese increases hardenability and tensile strength. But both nickel and manganese have been associated with potential toxicity effects:
Nickel
– Nickel is a common contact allergen. Nickel allergy affects 10-20% of the population. It causes skin irritation in those allergic to it.
– When stainless steel cookware containing nickel is heated, small amounts of nickel can leach into food. Consuming high doses of nickel has been linked to organ damage, birth defects, and cancer.
– The higher the nickel content, the more that leaches from cookware. Nickel release is highest when cooking acidic foods at high temperatures.
Manganese
– Manganese is an essential nutrient but high doses are toxic. Manganese toxicity can damage the brain and nervous system.
– Cooking acidic or salty foods in manganese-containing cookware can cause excessive manganese to leach at high temperatures.
– Manganese fumes released when welding high-manganese stainless steel may cause neurological problems with prolonged exposure.
So to avoid potential nickel and manganese toxicity, the stainless steel composition needs to be carefully evaluated.
Types of Non-Toxic Stainless Steel
304 Stainless Steel
304 stainless steel is the most common type used in kitchenware, appliances, and structural applications. It contains:
– Chromium: 18-20%
– Nickel: 8-10.5%
– Manganese: 2% max
While 304 stainless steel has high nickel content, studies have found nickel release is negligible if used properly for cooking. Acidic foods in 304 stainless steel only result in minor leaching if cooked at boiling temperature. 304 stainless steel cookware is generally considered safe if one is not allergic to nickel.
316 Stainless Steel
316 stainless steel has a similar composition to 304, but contains 2-3% molybdenum to increase corrosion resistance. This makes it suitable for salt water and chlorine environments. Like 304, studies indicate 316 stainless steel only leaches trace amounts of nickel during normal cooking. While sometimes more expensive, 316 stainless steel is also deemed food-safe for cookware.
201 Stainless Steel
201 stainless steel was developed as a lower cost alternative to 304, with reduced nickel content. It contains:
– Chromium: 16-18%
– Nickel: 3-5%
– Manganese: 5-6%
The lower nickel content helps minimize toxicity concerns. However, the higher manganese content means it may not be suitable for prolonged exposure to fumes when welding. It is commonly used in cookware, appliances, and hardware components. 201 provides good corrosion resistance at a lower cost but is a bit less durable than 304 or 316.
430 Stainless Steel
430 stainless steel is highly affordable and contains no nickel at all. It offers good corrosion resistance with its chromium content of 16-18%. However, ductility and toughness is limited due to less nickel. Applications are mostly in architectural trim, automotive trim, and appliances. 430 stainless steel cookware is an option but may be prone to denting.
100 Series Stainless Steels
The 100 series stainless steels like 101, 102, and 105 are ultra low nickel variants containing How to Identify and Choose Non-Toxic Stainless Steel
Since stainless steel composition varies, you need to identify which grade of stainless steel is being used for food contact and medical applications. Here are some tips:
– Examine product labels, packaging, technical specification sheets to find the exact type of stainless steel grade. Reputable manufacturers will disclose this.
– 100 series and 400 series grades will be non-toxic, 400 series has no nickel at all.
– 200 series and 300 series contain nickel but are acceptable if not allergic. 301 and 304 are common grades.
– Medical stainless steel is usually 316L grade for its corrosion resistance and low carbon content.
– Check certifications from reputable organizations like the FDA, NSF, and ISO to verify food-safe compliance.
– When in doubt, contact the manufacturer directly to ask about their stainless steel grade.
– For cookware, 100 series like grade 101 provide the best nickel reduction but 400 series like 430 are also good.
– Make sure cookware is well-made from reputable brands, cheap pots and pans are more prone to leaching metals.
So in summary, the most non-toxic stainless steel options would be:
– 400 series grades like 430
– 200 series grades like 201, 202
– 100 series grades like 101 which is very low nickel
– 316L and 304 will work as well for low leaching
Avoid cookware and products where the exact stainless steel grade is unknown. With a little bit of research, you can find the optimal non-toxic stainless steel variant for your specific application.
Tables Comparing Different Grades of Stainless Steel
Composition of Stainless Steel Grades
| Grade | Chromium % | Nickel % | Manganese % | Molybdenum % |
|---|---|---|---|---|
| 304 | 18-20 | 8-10.5 | 2 max | NA |
| 316 | 16-18 | 10-14 | 2 max | 2-3 |
| 430 | 16-18 | 0 | 1 max | NA |
| 201 | 16-18 | 3-5 | 5-6 | NA |
| 101 | 16-18 | NA |
Applications of Common Stainless Steel Grades
| Grade | Applications |
|---|---|
| 304 | Cookware, appliances, kitchen sinks, industrial equipment |
| 316 | Medical tools, pharmaceutical production, valves, pumps, marine components |
| 430 | Automotive trim, appliances, architectural applications |
| 201 | Cookware, appliances, automotive parts, industrial parts |
| 101 | Low cost cookware, appliances, automotive parts |
Health Risks of Stainless Steel Containing Nickel and Manganese
Nickel
– Skin irritation, rashes, redness, itching in those allergic
– Asthma symptoms may be aggravated
– Potential carcinogenic effects at high doses
– Organ damage if large amounts ingested
Manganese
– Neurotoxicity with prolonged inhalation exposure
– Parkinson’s disease-like symptoms
– Brain fog, forgetfulness, mood changes
– Impaired motor skills and reflexes
Tips for Safely Using Stainless Steel Cookware
– Use low or medium heat when cooking to minimize leaching
– Avoid cooking very acidic foods like tomatoes for extended periods
– Use sufficient cooking liquid to prevent direct metal contact
– Minimize use of chloride-containing salts that corrode stainless steel
– Use non-abrasive cleaners to keep the protective surface layer intact
– Use 100 series, 400 series, or well-researched 300 series cookware
Conclusion
Choosing a grade of stainless steel that avoids hazardous substances like nickel and manganese is key for food and medical uses. The most readily available non-toxic options are the 100 series (ex: 101), 400 series (ex:430), and possibly 300 series (ex: 304, 316) if nickel allergy is not a concern. Proper cooking practices also prevent leaching of any metals into food. With a little care selecting stainless steel composition and usage, you can reap the benefits of this versatile material while avoiding potential toxicity issues.