Toxicity Profiles

RAGs A Format for Zinc - CAS Number 7440666

Pure zinc is a bluish-white shiny metal. Zinc is one of the most common elements in the earth's crust and is found in air, soil, and water, and is present in all foods. Zinc has many commercial uses as coatings to prevent rust, in dry cell batteries, and mixed with other metals to make alloys like brass and bronze. A zinc and copper alloy is used to make pennies in the United States. Zinc combines with other elements to form zinc compounds; common zinc compounds found at hazardous waste sites include zinc chloride, zinc oxide, zinc sulfate, zinc phosphide, zinc cyanide, and zinc sulfide. Zinc compounds are widely used in industry to make paint, rubber, dye, wood preservatives, and ointments.

Zinc is an essential element with recommended daily allowances (RDS) ranging from 5 mg for infants to 15 mg for adult males. Too little zinc can cause health problems, but too much zinc is also harmful.

The digestive tract absorbs 20% to 80 % of ingested zinc based on the chemical compound ingested. Harmful health effects generally begin at levels in the 100 to 250 mg/day range. Eating large amounts of zinc, even for a short time, can cause stomach cramps, nausea, and vomiting. Taken longer, it can cause anemia, pancreas damage, and lower levels of high-density lipoprotein cholesterol (the good form of cholesterol). Breathing large amounts of zinc (as dust or fumes) can cause a specific short-term disease called metal fume fever. This is believed to be an immune response affecting the lungs and body temperature. The long-term effects of breathing high levels of zinc or the effects on human reproduction are not known. Rats that were fed large amounts of zinc became infertile or had smaller babies. Irritation was also observed on the skin of rabbits, guinea pigs, and mice when exposed to some zinc compounds. Skin irritation will probably occur in humans.

No case studies or epidemiologic evidence has been presented to suggest that zinc is carcinogenic in humans by the oral or inhalation route. In animal studies, zinc sulfate in drinking water or zinc oleate in the diet of mice for a period of one year did not result in a statistically significant increase in tumors; however, in a 3-year, 5-generation study on tumor-resistant and tumor-susceptible strains of mice, exposure to zinc in drinking water resulted in increased frequencies of tumors. Zinc is placed in weight-of-evidence Group D, not classifiable as to human carcinogenicity due to inadequate evidence in humans and animals.

The following is a presentation of the toxicity information associated with Zinc.

• The Oral Chronic Reference Dose is 3.00E-01 (mg/kg-day).
• The Oral Chronic Reference Dose has a modifying factor of 1.
• The Oral Chronic Reference Dose has an uncertainty factor of 3.
• The Oral Chronic Reference Dose is based on the Yadrick et al study from 1989.
• The Oral Chronic Reference Dose study critical effect is 47% decrease in ESOD concentration in adult females after 10 weeks.
• The overall confidence in the Oral Chronic Reference Dose is medium.

• The Dermal Chronic Reference Dose is 6.00E-02 (mg/kg-day).
• The Dermal Chronic Reference Dose is based on a gastrointestinal absorption factor of 0.2000.

• The Oral Chronic Reference Dose is 5.00E-02 (mg/kg-day).
• The Oral Chronic Reference Dose has a modifying factor of 5.
• The Oral Chronic Reference Dose has an uncertainty factor of 100.
• The Oral Chronic Reference Dose is based on the Howard and Hanzal study from 1955.
• The Oral Chronic Reference Dose study critical effects are weight loss, thyroid effects, and myelin degeneration.
• The overall confidence in the Oral Chronic Reference Dose is medium.

• The Dermal Chronic Reference Dose is 1.00E-02 (mg/kg-day).
• The Dermal Chronic Reference Dose is based on a gastrointestinal absorption factor of 0.2000.

• The Oral Chronic Reference Dose is 3.00E-04 (mg/kg-day).
• The Oral Chronic Reference Dose has a modifying factor of 1.
• The Oral Chronic Reference Dose has an uncertainty factor of 10000.
• The Oral Chronic Reference Dose is based on the Bai et al. study from 1980.
• The Oral Chronic Reference Dose study critical effect is reduction of food intake and body weight.
• The overall confidence in the Oral Chronic Reference Dose is low.

• The Dermal Chronic Reference Dose is 6.00E-05 (mg/kg-day). The Dermal Chronic Reference Dose is based on a gastrointestinal absorption factor of 0.2000.