As an expert in the field of environmental health and toxicology, I can provide you with a comprehensive understanding of the potential health effects of nickel on humans.

Nickel is a naturally occurring element that is found in the Earth's crust and is widely used in various industrial applications, including the production of stainless steel, batteries, and electronics. It is also used in jewelry and coins, which can come into direct contact with the skin. The health effects of nickel on humans can vary significantly depending on the form of nickel, the route of exposure, and individual sensitivities.

**Non-Sensitive Individuals and Dietary Exposure**
For individuals who are not allergic or sensitive to nickel, the risk of experiencing adverse health effects from dietary intake is quite low. The human body can tolerate small amounts of nickel without any significant health consequences. However, if a person were to consume very large amounts of nickel, it could potentially lead to harmful health effects. This scenario is highly unlikely under normal circumstances, as the amount of nickel typically found in food is not sufficient to cause harm.

Nickel Allergies and Skin Contact
A more common concern with nickel is the potential for allergic reactions. Some individuals have a sensitivity to nickel, which can result in contact dermatitis—a type of skin inflammation that occurs when the skin comes into contact with an allergen. This is particularly relevant for people who wear jewelry containing nickel, as the metal can cause rashes, redness, and itching on the skin. In such cases, avoiding contact with nickel is the best course of action to prevent allergic reactions.

Inhalation Exposure
Another route of exposure to nickel is through inhalation, which can occur in occupational settings where workers are exposed to nickel dust or fumes. Long-term inhalation of nickel particles can lead to respiratory issues, including lung damage and potentially lung cancer. Workers in industries such as metal refining, welding, and battery manufacturing are at a higher risk and must adhere to strict safety protocols to minimize exposure.

Nickel Compounds and Carcinogenicity
The International Agency for Research on Cancer (IARC) has classified certain nickel compounds as carcinogenic to humans. This classification is based on evidence that suggests a link between exposure to specific nickel compounds and an increased risk of cancer, particularly lung and nasal cavity cancers. Metallic nickel, on the other hand, has been classified as possibly carcinogenic to humans, indicating that there is limited evidence of carcinogenicity in humans but sufficient evidence in animals.

Precautions and Regulations
To protect public health, many countries have regulations in place to limit the amount of nickel that can be present in consumer products, especially those that come into contact with the skin, such as jewelry. There are also occupational safety standards to protect workers from excessive exposure to nickel in the workplace.

Conclusion
In summary, while nickel itself is not inherently harmful to all humans, it can pose health risks to certain individuals, particularly those who are allergic or sensitive to it. Additionally, specific nickel compounds have been identified as carcinogenic, and metallic nickel is considered possibly carcinogenic. It is important for individuals to be aware of their sensitivities and for industries to follow safety guidelines to minimize exposure and protect health.

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People who are not sensitive to nickel must eat very large amounts of nickel to suffer harmful health effects. ... The International Agency for Research on Cancer (IARC) has determined that some nickel compounds are carcinogenic to humans and that metallic nickel may possibly be carcinogenic to humans.read more >>