Zinc in Soil
What is Zinc?
Zinc is one of the most common elements in the world as it naturally
occurs in the earth’s crust and is found in air, soil, water, and is
present in most foods. Zinc can also enter the environment from a
variety of human activities such as mining, steel production, coal
burning, and burning of waste. Although zinc does not dissolve in
water, it can build up in fish and other organisms but does not build
up in plants.
How could I be exposed to Zinc?
Similar to lead and other metals, zinc primarily enters the body by
mouth (orally) through food, water or by small soil or dust particles.
Young children are most likely to ingest zinc from dirt or dust via
hand-to-mouth habits. Zinc can also be inhaled (from zinc smelting
or welding operations) and is less commonly absorbed through the
skin.
What level is considered to be dangerous?
Under the Ontario Environmental Protection Act, a residential
and parkland standard has been set for zinc in soil at 600μg/g.
Higher levels of zinc in soils do not automatically constitute a
health risk. The minimum risk level, where negative health effects
are observed, for chronic oral exposure is 0.3 mg/kg of body
weight per day. However, this assumes long-term exposure to
contaminated soils over many years. Levels of zinc recommended
for healthy dietary intake are significantly lower than this level and
are usually achieved through a proper diet and/or supplementation.
What are the health effects or symptoms of
zinc poisoning?
Large doses of zinc (at levels 10–15 times higher than
recommended dietary intake) taken by mouth even for a short time
can cause stomach cramps, nausea, and vomiting. Chronic exposure
to high doses can cause anemia, damage your pancreas and
decrease the levels of your good cholesterol. The risk and health
outcome will also vary depending on the individual, the circumstances,
and the amount of soil ingested. Minor skin irritation can occur
from contact with high levels of zinc but is usually associated with
occupational exposure (i.e. working with zinc compounds).
Who is most at risk?
Aside from occupational exposures, infants and young children are the
most susceptible to high levels of zinc because they more commonly
put non-food items and their dirty hands in their mouth. Furthermore, as
they are not fully developed, young children generally are at greater risk
than adults to environmental exposures.
Should I take my child to the doctor for testing?
If you have a reason to suspect zinc poisoning, tests can be conducted
at most doctors offices and clinics. These tests usually involve blood,
urine or feces samples sent to the lab to determine if high levels of
zinc exist in your or your child’s body. However, the levels found in
fluids or feces will include all sources of zinc including from food and
supplements. There are upper and lower limits to how much zinc
should be taken via diet for different age groups and whether you are
male or female. Your doctor or local Public Health Nutritionist will
have this information.
How can I minimize exposure to zinc from soil?
• Discourage your children from putting their hands or objects in
their mouth when playing outside and teach them to wash their
hands upon returning home especially before eating
• Remove outdoor footwear before entering your home and launder
clothing with visible dirt stains
• Brush pets coats after taking them for walks in areas where they
may be exposed to soil or open ground (i.e. not paved)
The Ontario Ministry of the Environment, Health Canada, and the U.S. Agency for
Toxic Substances and Disease Registry were informed of the development of this
fact sheet.
Region of Waterloo Public Health
Health Protection and Investigation
519-883-2008
www.regionofwaterloo.ca/ph
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519-883-2000
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TTY 519-883-2427
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Fax 519-883-2241