Many people are not aware of the toxic nature of plastic mulch and using other plastics (such as polytunnels) in growing food. So here’s some info that I collated for you, posted originally by my friend Mike Hoag, with plenty of academic references for you:
Exactly How Bad is Phthalates Risk from Plastic Mulch, Landscaping Fabric, Tarping and Solarizing?
So, here’s a shocking story. Researchers publishing in The Journal of Exposure Science and Environmental Epidemiology wanted to find out how much phthalates exposure was coming from food, rather than other sources.
So, they tested 10 families for phthalates baselines. Like most Americans, their levels exceeded the EPA’s (notoriously industry friendly) limits for reproductive and testicular health by as much as 4 times. (People wonder why T levels for men are now 1/4 what they were through our evolutionary history.)
Then the researchers set the families on an all-organic, unprocessed detox diet and made sure that the food never touched plastic. All food was from local organic farms, stored, and shipped in glass to eliminate any plastic contact from shipping and storage.
And… **their phthalates levels went through the roof. **Exposure to the most dangerous phthalate went up by nearly 20 times. Unexpected results in a randomized dietary trial to reduce phthalate and bisphenol A exposures - PubMed
While the researchers found this “unexpected,” folks familiar with modern organic farming might not be so surprised. Increasingly, organic farmers are pressured to use plastic to compete with conventional growers using herbicides, and as more adopt more plastics, it increases pressure, causing a race to the bottom.
So researchers tested the food and found the phthalates were coming from the growing process on the farms. Much came from soils contaminated with plastic contact.
Researchers investigating the phthalates source in dairy found that hand-milked dairy had very low levels of phthalates, but cows machine-milked with plastic tubing had very high levels of phthalates. **Just that brief exposure to the plastic tubing was enough to contaminate the milk. **
Here’s the thing about phthalates. They are very volatile and can leach at a high rate when exposed to environmental conditions, heat, wet, movement, and biological activity.
And while phthalates have an affinity for fats, giving meat and dairy consistently high levels (especially chicken!) in one study adults eating a diet high in fruits and vegetables had similar phthalates levels to those eating a diet high in meat and dairy (both were well over EPA safety limits, EPA limits for testicular health and limits for birth defects.) Phthalates and diet: a review of the food monitoring and epidemiology data - PubMed
So it is not enough to eat organic, eat local, avoid processed foods, or grow our own. HOW the food is grown matters, too.
And yes, finally, we have good research showing that agricultural plastics are the source of this phthalates. The analysis above includes links to studies showing that plastic hoophouses, landscaping fabric, and plastic mulches especially cause phthalates contamination and uptake into the plant tissues. We also know that food grown in soil WITHOUT plastic, but in areas with contact to plastics, such as near plastics plants, or where hoop houses or plastic mulches had been used in the past, will also have phthalates in them.
This link is now fixed - paper, ‘Critical Review on the Presence of Phthalates in Food and Evidence of Their Biological Impact’, download full text at this address:
https://www.researchgate.net/publication/343462436_Critical_Review_on_the_Presence_of_Phthalates_in_Food_and_Evidence_of_Their_Biological_Impact
But researchers in that study are calling for more research on exactly how long exposure and what conditions increase phthalates contamination. We don’t really know how long a silage tarp has to be on the ground or in what conditions to contaminate the soil with phthalates, and then how long the phthalates take to break down.
So, until that research comes in, if you want to reduce your phthalates load, my recommendation is use (or find farmers who use) alternative methods to tarping, or use materials like old canvas tarps and dropcloths made from natural fibers. And of course, to educate about plastics in food, so that good growers will feel less pressure to adopt unsafe techniques.
Another paper, ‘Risk Assessment of Agricultural Plastic Films Based on Release Kinetics of Phthalate Acid Esters’:
pubs.acs.org/doi/10.1021/acs.est.0c07008?
Phthalates are coming from our farms and gardens
We talk about avoiding plastics a lot in this group.
If you want an up-to-date overview of phthalates contamination in food, this is a really great 2020 paper. As far as academic reading goes, it’s pretty accessible.
A few really interesting takeaways for those of us in Permaculture:
—Phthalates are considered a significant risk to human health, with proven risks to our reproductive systems, brain health, cancer risks, immune systems, and metabolisms.
—Food is one of our major exposure risks to phthalates, and phthalates bioaccumulate so the key is to avoid as much exposure as possible. Older materials supposed that cosmetics were our major source, so this is still often repeated in farming and hyrdopnics groups that promote Ag plastics. This is no longer considered true, and food is now considered our single largest exposure, with over 67% of phthalates coming from food.
—Agricultural plastics like plastic films and greenhouses are major risks, and plants uptake these chemicals from these plastics at rates considered over acceptable safety levels.
—Phthalates can be absorbed by plants directy from the air, and plants grown under plastic films, row covers, and hoop houses had significantly higher levels of phthalates, especially in leafy vegetables.
—Working in greenhouses poses special additional risk.
—Olive oil is loaded with phthalates, compared to other oils! Why? Because they are perennial, and perennials have greater ability to bioaccumulate. The phthalates are entering the system from the production, not storage and transport, so the likely source is plastic films common in olive orchards. This means plastic tarps and covers in perennial systems like orchard trees are likely a significant risk.
—Phthalates have been found to uptake into fruits.
—Phthalates levels in dairy, and alcoholic beverages are also very high.
—Ag plastics used in the production of grapes was considered one likely source in wines, so the phthalates are coming from what we’re doing on farms.
Paper: ‘Critical Review on the Presence of Phthalates in Food and Evidence of Their Biological Impact’:
Whenever I talk about plastics risks on the farm, I get messages asking about ”the farmer’s friend,” silage tarps. Using tarps to clear fields to avoid tilling has become almost THE gardening method of the regenerative movement.
Many folks recommending (and selling or taking commission on) tarps are using PVC tarps. If PVC is flexible, like a tarp, then it is almost certainly loaded with phthalates. These PVC materials have been found to have the highest rates of phthalates and the highest rates of leakage, and breakdown to microplastics.
So many sellers of silage tarps for weed suppression have switched to LDPE with the claim that these are perfectly safe and contain no phthalates.
First, in actual studies of these materials, this has not been found to be true.
But more importantly, plastics are “complex mixtures of extractable chemicals that can be toxic.” While many are claiming their silage tarps are perfectly safe, this 2021 study assessing various plastics found LDPE products actually had the HIGHEST rate of potential toxicity, including endocrine disrupting chemicals. So when people claim their silage tarps are “safe,” what they are really claiming is that theirs do not knowingly contain the most studied and confirmed dangerous chemicals. In other words, we do not specifically know exactly how unsafe these materials are.
Paper: ‘Plastic Products Leach Chemicals That Induce In Vitro Toxicity under Realistic Use Conditions’:
https://pubs.acs.org/doi/10.1021/acs.est.1c01103
The same goes for non-plastic biodegradable mulches and tarps. These have been found to have even higher rates of endocrine disruptors than actual plastics.
So no, I would not consider any silage tarps safe for gardening use.
I do not personally like or use this gardening technique anyway, as I find it to be just far more work, and it creates far too many problems than just good classic French Intensive or BioIntensive style garden management techniques, slashmulch, or deep mulch gardening. But at present I do not recommend any silage tarps as safe. If I HAD to do this for some reason, I would use cardboard or fabrics made of natural materials like canvas, without flame retardants, or coatings.
I don’t have any antique gardening tools but some of my other tools are. Often really high quality and very functional! I even have a lovely American hammer, with a lovely leather grip. Well, not antique but quite a few decades old! Top brand that they still make now, but now they put a toxic lacquer into the leather to ‘protect’ it! Screw that! And a saw with brass fittings, things like that. For me they are just way nicer to look at and use than ones with plastic handles that look horrible, feel gross, and will degrade in a few years!
Can’t be healthy!
I do feel somewhat optimistic because Earth started as toxic to humans and most liveforms. Although humans have really messed it up it still isn’t anything nature can’t handle in long term. There are some bacteria that have evolved to break down plastics for example. In human timeframe it’s still unpleasant both for humans and nature.