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Commonly used gardening materials – the risks and how to avoid them

Being a frugal gardener requires resourcefulness and creativity. Soil, lumber, starter plants and other materials can all add up in cost. However, before you repurpose any materials or opt for plastic, it's a good idea to do some research.
Different types of plastics, metals, lumber and other materials can carry a variety of risks. It's worth looking into if you're planning to grow food in unconventional containers or beds. To help out, we've provided a list of materials commonly used for gardening and some risks they pose.
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1. PVC pipe and other plastics
PVC pipe is easy to manipulate and very cost-effective. But it's not considered the safest in terms of using it to grow food. According to Walden Labs, most PVC contains chemicals, which when heated can leach out of the plastic and into the soil. So it might be best to use PVC pipe for hoop houses, hose reels and other projects where the plastic doesn't contact the soil. Still, there are some plastics that are good options for gardening. The Micro Gardener suggests referring to the recycle number (the one inside a triangle) and avoiding anything labeled with a 3 (PVC), 6 or 7. Numbers 1, 2, 4 and 5 are generally considered safe. This includes milk jugs, 2-liter bottles and typical plastic pots you might buy at the store.
2. Cinder blocks
Cinder blocks are cheap, and you can build so many different types of structures with them. Unfortunately, however, gardening with cinder blocks may pose a threat to your health. According to Natural News, cinder blocks are made using a combination of Portland cement and fly ash. Fly ash is a byproduct of coal combustion and likely contains harmful heavy metals that end up sealed into the blocks. These heavy metals could leach into the soil and into your food. Not all cement shares this same threat, so do your research. Cement, in general, can still be a possible option for gardening. Your best bet, however, is to use natural, untreated stone, pavers or bricks.
3. Rubber tires
Rubber tires are another popular material used in the garden, and for obvious reasons. They are easy to get for free, and you can combine them into whatever structure you want. As far as using tires as containers, Cheryl Long from Mother Earth News says that's probably okay on a short-term basis. Long term, however, rubber tires have the potential to leach PAHs (polycyclic aromatic hydrocarbons), which are known carcinogens. It's probably best not to use tires to plant edibles. Consider an alternative instead, like using food-grade barrels (make sure they're made of the safer plastic) cut into sections instead.
4. Lumber
Lumber is probably the most popular material used for gardening projects. Generally, it's best to pick unpainted, untreated, rot-resistant woods, such as cedar. But pressure-treated lumber is considered safer than it used to be. According to Gardens Alive, lumber used to be treated with CCA (copper, chromium and arsenic). For obvious concerns about the leaching of these chemicals, pressure-treated lumber was considered unsafe for growing edibles. Now lumber is treated with copper and ammonium chloride. Although said to be safer than CCA, these chemicals (copper, ammonia and chlorine) are still hazardous to human health. So it's probably best to avoid them for gardening. If you still want to use pressure-treated lumber over natural, rot-resistant lumber, look into lumber treated with boric acid, which is reportedly safe for humans. You could also consider using composite wood, made from recycled plastic (make sure it's the safer kind).
5. Galvanized metal
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Galvanized metal is definitely trending in home gardens. Large troughs make rustic, charming containers. As far as the safety of the material goes, there doesn't seem to be much to worry about. The U.S. General Services Administration defines galvanized metal as metal that has been coated with zinc to help protect it from rust. According to Rodale's Organic Life, while there is evidence that zinc and other chemicals in galvanized metal do leach into the soil, the amounts are very small and unlikely to cause any harm. Not to mention, zinc is slow to move through soil and usually stays in the immediate area of the metal. Also, zinc's availability to plants is often limited by a number of factors, including soil pH, which means it's unlikely you could ingest too much from eating plants. The important thing here is to know the history of the metal you're using: Whether it was used to store toxic materials and what it has been treated with are the types of things you will want to know. And avoid rusted or corroded structures. Overall, do your due diligence before deciding on using metal to grow your food.
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