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Mercury in the Garden

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thermometerMercury

Sources of mercury exposure

Sources outside the garden are typically greater health
risks. Mercury is usually found at very low levels in
soils, but hotspots from man-made sources may also
exist. Below are some of the main sources of mercury
exposure, both in and outside the garden.

Factory icon nearby industry – Coal power plants,
mining operations, and other industries
can release the metal into air, water, and
soil.
Fish icon fish Highly toxic methylmercury can
build up in the food chain, as one fish
eats a smaller fish.
Stream icon aquatic environments Peaty and
waterlogged soils have the highest
concentration of naturally occurring
mercury.

Mercury types

Exposure to mercury in the garden
How am I exposed? You can be exposed by eating or breathing contaminated soil particles, or by eating contaminated garden produce.

Are my garden plants safe to eat? Soils tend to contain inorganic mercury. Plants (and people) are not good at absorbing mercury in this form. Garden produce is not a major source of mercury exposure.

Should I be worried? It is important to remember that there are many health benefits associated with gardening. Mercury exposure is a serious concern in mining communities and among communities that eat certain types of fish. However, garden exposure at high levels is uncommon. Even so, limiting exposure, especially for children, is always a good idea.

Limit children’s exposure

Child with buckets
  • Small doses matter. Children breathe, eat, and drink more relative to their size than adults
  • Their bodies and brains are still developing
  • Children spend more time on the ground and often put things (like dirt) into their mouths
  • They have more skin surface area than adults, so skin exposure also matters

Making sense of regulatory standards
No official standards have been established in North Carolina for acceptable levels of mercury in garden soils. For remediating residential soil, North Carolina uses EPA guidelines for different forms of mercury. New York State’s guideline (0.81 ppm*), considers exposures like gardening and assumes mercury is in its most toxic form, so it is a conservative value that represents an abundance of caution.

Chart

Health impacts of mercury
Exposure to inorganic mercury at high levels can damage kidneys, stomach, and intestines. Impacts to the nervous system can cause mood swings, memory loss, and behavioral changes. Skin exposure can cause rashes and dermatitis.
Children and pregnant women are at greatest risk from mercury exposure. The developing fetus is vulnerable to the toxic effects of maternal mercury exposure.
Methylmercury is particularly toxic and can accumulate up the food chain, but it is not usually found in garden soils.

Reduce mercury exposure in the garden

  • Uptake of mercury by plants is low, so focus on controlling dust and limiting soil ingestion
  • Remove boots or shoes after gardening to reduce the amount of contaminated soil you track into your home
  • To reduce mercury particles in air from dust, cover bare soil with mulch and keep the soil moist
  • Flooded soils may help convert mercury to its more toxic form, but this can take many months
  • Adding compost or other organic matter from a contaminant-free source may help dilute mercury concentration in soil. Check the NC Composting Council website to find STA or OMRI certified compost
  • Conduct a soil safety training for all garden users on exposure reduction strategies
  • Visit our website below for our factsheet on 10 Healthy Garden Habits

Testing Resources

Plant icon How to test your soil and interpret the results
Sun More Information
Question icon Still have questions about mercury soil testing? Email us at superfund@duke.edu.

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This work was supported through the National Institute of Environmental Health Sciences P42 Multiproject Center Grant program, grant number P42ES010356.