Stainless steel is rightly recommended as the safest workhorse. The honest qualification: it's an alloy, and alloys leach metals — especially under acidic, prolonged-cook conditions. For the general population the leach quantities are well below regulatory thresholds. For people with diagnosed nickel allergy or systemic nickel allergy syndrome (SNAS), the exposure is meaningful.
Kamerud 2013 — the canonical stainless leach study
Kamerud, Hobbie & Anderson (2013, PMID: 23984718) cooked tomato sauce in stainless steel for 6 hours. Nickel concentration rose up to 26-fold; chromium up to 7-fold. After 20 hours, Ni rose 34-fold and Cr 35-fold. New pans leached most. Leaching stabilized after ~6 cooking cycles. Tenth-cycle leach: average 88 µg Ni and 86 µg Cr per 126 g serving.
For context: WHO Tolerable Daily Intake for nickel is 13 µg/kg body weight per day. A 70 kg adult's TDI is 910 µg. The Kamerud 10th-cycle figure of 88 µg/serving is ~10% of TDI — meaningful for sensitized individuals, marginal for the general population.
Nickel allergy is common
Ahlström et al. (2019, PMID: 31140194) — nickel allergy general-population prevalence: 8–19% adults in Europe, 17.5% North America (NACDG 1994–2014). Women are 4–10× more affected than men. Nickel is the single most common contact allergen worldwide.
Systemic Nickel Allergy Syndrome (SNAS)
Rizzi et al. (2014, PMID: 24674689) — SNAS presents with GI symptoms (often misdiagnosed as IBS) plus cutaneous signs in nickel-sensitized patients with dietary nickel exposure. Avoiding nickel-leaching cookware is part of the standard management protocol.
Plain-language summary on stainless
Most people are fine cooking tomato sauce in stainless. If you have nickel allergy, contact dermatitis, or unexplained IBS-like symptoms, consider 18/0 stainless (nickel-free), Demeyere's Silvinox-treated 18/10 (lowest-leach), well-seasoned cast iron, or glass for acidic long-cook applications.
Cadmium in ceramic glazes
Cadmium glazes are typically yellow, orange, and red — the same colors consumer brands love.
Demont et al. (2012, PMID: 25526575) — EU survey of ceramics and glassware tested for lead and cadmium release. Detectable cadmium leach in a non-trivial fraction of decorative glazed items. Red and yellow glazes overrepresented.
IARC classifies cadmium and cadmium compounds as Group 1 (known human carcinogen) — primarily lung cancer via inhalation. Oral exposure is renal and skeletal: chronic low-level cadmium causes irreversible renal tubular damage. Half-life in renal cortex is 20–30 years.
FDA CPG Sec. 545.400 sets cadmium action levels: flatware 0.5 µg/mL, small hollowware 0.5 µg/mL, cups/mugs 0.5 µg/mL.
Itai-itai disease — historical reference
Toyama, Japan, 1912–1965. Chronic dietary cadmium exposure from contaminated rice caused osteomalacia plus renal failure in a documented population. This is the gold-standard mechanistic proof that chronic dietary cadmium causes harm. Not from cookware — from contaminated water and rice — but the dose-response is established.