Reduce Lead in City Gardens

Backgrounder

Many substances pollute the air around us, particularly in cities. Some chemicals even get into our garden soil and plants, and these can affect our health. One is of these is lead. We may not see or taste it, but some crops grown in cities may contain dangerous amounts of lead. So we need to protect our urban gardens and ourselves from getting too much.

Lead reaches plant leaves and gets into the soil in two main ways. Some lead comes from car and truck exhaust. Many gasolines contain a form of lead. The lead in exhaust travels in the air and settles on soil and plants.

Some paints have lead in them. An old house may have been painted many times. The paint scraped off when a house is repainted is often left on the ground where the paint chips break down and lead is washed into the soil by rain. Demolished houses or buildings also leave paint chips on the ground.

The dangers are real. If too much lead enters our bodies from eating contaminated crops, we may get headaches, anemia, blindness, kidney disease, paralysis, even brain damage. Severe lead poisoning can sometimes cause death.

Young children are most affected by lead because their bodies are small and still growing. Lead is more easily absorbed during periods of rapid growth. Pregnant women and nursing mothers should also take great care as the growing baby is very susceptible to lead damage. Lead crosses the placenta and will reach an infant through breast milk.

But there are many things you can do to protect your garden from lead contamination. Lead travels in dust particles. If you build some kind of barrier between your garden and the road, you can stop some of the dust from reaching your crops. For example, grow a hedge of tall shrubs or trees. Or build a fence high enough to prevent dust from rising over it. Also, plant sunflowers (Helianthus spp. esp.H. Annuus) or morning glories (Ipomoea purpurea) beside the barrier or closer to the road than other crops to help absorb lead from the air.

Plant your garden as far away from the road as possible, especially if there is a lot of traffic. More than 45 metres away is best. If your garden is located within 15 metres or less of a busy street, plant vegetables in containers such as pots or trash cans. Fill them with clean topsoil. You may want to remove the old soil and replace it with new soil.

Some crops absorb less lead from the soil and air than others. Fruiting crops such as beans, tomatoes, peppers, eggplant, squash, cucumbers, and melons are the safest ones to plant. The edible parts of these crops do not absorb much lead. And lead from the air settles on the leaves which we don’t eat. The next best crops to plant are root crops like carrots, onions, and beets. Leafy crops such as kale, chard, lettuce, celery, mustard, spinach, and herbs are the most dangerous to grow in the city because we eat the leaves of these crops, which is where a lot of the lead goes. Cabbage is safer than other leafy vegetables because it has a tight head and grows from the inside out.

If you wish to plant a variety of crops in your city garden, plant leafy greens and other vegetables that are hard to wash farthest from the road. Next, plant root crops. Place your fruit crops in the area of your garden closest to the road.

You can also reduce lead by managing your soil. There are many ways to treat your soil to protect against lead.

Spreading mulch is a good idea. Mulch is a barrier that protects the soil and stops lead in the air from settling directly onto it. Mulch also reduces dust and keeps soil moist. Use a six inch layer of mulch such as leaves or hay on top of your soil. Mulch will also add nutrients to the soil as the organic matter breaks down. Mulching can also be done with black plastic sheets, or newspaper. But do not use coloured newspaper because it contains lead.

Another way of treating the soil is to add well decomposed organic matter such as compost, kitchen vegetable wastes, or rotted manure as often as possible. Lead sticks to organic material and stays away from plant roots. And organic matter improves the soil structure and provides nutrients for your plants.

You may add lime to raise the acid content of your soil called the pH balance. Soil pH above 6.5 will cut down the amount of lead your plants take up. And pH of 6.5 is a normal level for growing vegetables. If possible, before planting a garden, have your soil tested for lead and for pH balance. Take a handful of soil in a clean container to the nearest extension service. They should be able to find a place to get it tested.

Once your vegetables are harvested and you are ready to eat them, take off the older, outside leaves. Wash vegetables thoroughly in water with a little vinegar or dish soap added. Washing only with water will not remove all the lead.

Peel all root crops to remove lead that may have concentrated in the peel. But remember, the peels of vegetables such as carrots contain many nutrients. Scrubbing or peeling reduces the amount of vitamins they contain.

And remember, to protect soil from lead based paints, always be careful when painting or chipping off old paint near your garden soil.

With a little care, you can reduce lead in your garden and grow safe, nutritious crops.