Nickel

Nickel's industrial rise accelerated in the late 19th century when it was adopted for coins (the US nickel was introduced in 1866), armor plating, and later stainless steel — nickel makes steel resistant to corrosion [1]. The toxic story intensified through the 20th century in the nickel refining industry: workers at nickel refineries in Wales and Canada had lung and nasal cancer rates three to five times normal, leading to nickel compounds being classified as Group 1 human carcinogens [2]. Today, nickel enters the environment from burning fossil fuels (particularly heavy fuel oil and coal), nickel mining and refining operations, and municipal waste incineration. Nickel is a ubiquitous industrial metal — it is in the stainless steel of your cookware, your phone's battery, your jewelry, and the coins in your pocket [3]. Cigarette smoke is a meaningful nickel delivery system: tobacco plants absorb nickel from soil and concentrate it in smoke.

For the general population, food is the primary intake route — whole grains, legumes, nuts, seeds, and chocolate contain moderate levels of nickel [1]. Acidic foods cooked in stainless steel cookware can leach small amounts of nickel. Direct skin contact with nickel-containing metals is the cause of nickel allergy: earrings with nickel posts, watchbands, belt buckles, jeans buttons, and bra clasps are the classic sensitizers. Once sensitized, even trace nickel contact can trigger an eczematous rash [2]. Inhalation matters for workers in nickel refining, electroplating, battery manufacturing, stainless steel welding, and copper-nickel smelting — these represent the high-cancer-risk exposures. Diesel exhaust and ambient air in industrial areas contain nickel particles. Dental appliances, orthopedic implants, and some medical devices contain nickel alloys [3].

The cancer evidence for nickel compounds is unambiguous for lung and nasal cavity cancers in occupationally exposed workers [1]. The mechanisms involve nickel compounds entering cells, inhibiting DNA repair, and generating oxidative damage — soluble nickel compounds and nickel subsulfide are the most genotoxic forms. At lower exposures, the dominant health effect is allergic sensitization: nickel is responsible for roughly 20% of all contact dermatitis cases, affecting an estimated 15% of women and 3% of men in developed countries [2]. Systemic nickel allergy — where oral exposure to nickel through food triggers eczema outbreaks — is increasingly recognized and affects people who become sensitized through ear piercing or prolonged skin contact. Nickel fume inhalation at high acute doses causes metal fume fever with flu-like symptoms, and chronic inhalation causes chronic sinusitis and nasal perforation [3].

People with pierced ears — especially those whose piercings were done with nickel-containing jewelry — are the group most commonly sensitized to nickel [1]. Women are sensitized more frequently than men, largely due to jewelry exposure. Workers in nickel refining, smelting, electroplating, and stainless steel welding face the highest cancer risk — particularly those with inhalation exposures to nickel sulfide and oxide fumes [2]. Individuals who have received nickel-containing orthopedic implants or dental appliances may develop systemic reactions. Children with nickel allergy need to be kept away from nickel-containing toys and clothing fasteners, which remain common despite regulations in Europe.

If you have a known nickel allergy, choose surgical steel, titanium, niobium, or gold (14k or above) for jewelry, piercings, and eyeglass frames [1]. Use a nickel-detecting spot test kit on metal jewelry before purchasing. Switch to plastic or coated metal for belt buckles, watch clasps, and jeans buttons. If your hands are frequently in contact with nickel surfaces, use barrier gloves [2]. For dietary nickel reduction (if you have systemic nickel allergy): limit whole grains, legumes, chocolate, and nuts consumed in large quantities. Choose cast iron or enameled cookware over stainless steel for acidic dishes. Workers in nickel-exposure industries should use local exhaust ventilation, NIOSH-approved respirators during refining and welding operations, and undergo periodic lung function testing [3].