The Great Healthy Yard Project: a talk at the Wilton Library

Lewis' book
Lewis’ book

Last night we heard a talk by Diane Lewis, MD on The Great Healthy Yard Project (their web site is, run by Lewis from her home in Bedford, NY. Trained as a nephrologist (kidneys) and an internist, Lewis is not currently practicing medicine but devoting her time to promoting her project: reducing groundwater pollution by reducing the use of lawn chemicals. The talk was co-sponsored by Wilton Go Green, the Wilton Conservation Commission and the Wilton Garden Club, who introduced the speaker. The talk was recorded and will soon be on the Wilton Library’s website.

Lewis has also written a book on this issue with the same title, which is available on Amazon. She also has published articles summarizing her views in the New York Times and in the Baltimore Sun. A short 3-minute video on the tghyp website summarizes her position.

Lewis’ thesis is that “chemicals” from our lawns and gardens run off into the groundwater and eventually are found in our drinking water. As to which chemicals are of greatest concern, Lewis was quite vague as she mentioned none specifically. Were insecticides of more concern than fertilizers? Probably, but she didn’t actually say so.

She noted that the EPA is quite concerned about this runoff claiming that there is runoff in 70% of streams. The EPA does have a page with good and specific recommendations here. You can also find good descriptions of the problem at the US Geological Survey web site.

Lewis feels that this runoff into our drinking water is a serious problem and that it may be cumulative and could “damage our DNA,” although she presented no evidence for this somewhat surprising conclusion.

Endocrine disruptors

Central to her argument is that these (unspecified) chemicals are endocrine disruptors which even at very low levels may cause harm to humans. The whole idea of endocrine disruptors is controversial, however, and has not been definitively established.

The Endocrine Society has published two reports in this area. The 2009 report described the problem but noted that “Unfortunately, it is virtually impossible to make direct links between such epidemiological observations and exposure to given chemicals.” And, a key scientific paper in Science was withdrawn because of apparent scientific misconduct.

Needless to say, there are naysayers in this area, and one published by criticizes the Endocrine Society, but this report was published by a manufacturer’s group, the American Chemistry Council.

Lewis suggested that these endocrine disruptors could be the cause of increased breast cancer, prostate cancer, diabetes, ADHD and autism, but really offered no science to support these views. When I talked with her afterwards, she said there were papers on rats showing that they take on autistic symptoms after treatment with some “chemicals,” but did not cite one specifically. She suggested that these chemicals could be one of many contributing causes, and this is borne out in papers (also here and here). But one problem with this hypothesis is that recent work shows that there has been no increase in autism occurrence in the past 30 years.

Confusion and misinformation

In her gardening segment, Lewis lost ground with reality by suggesting somehow that “eating organic food” would be beneficial, even though there is no evidence that organic food is more nutritious, tasty or safer in any way.  In fact, the classic paper by Bruce Ames showed that the toxic and carcinogenic pesticides generated by plants themselves were present at a level 10,000 times higher than any pesticide residues.

She also suggested that the decline in Monarch butterflies was caused by the planting of “GMO” crops, but backed off when I pointed out that large agriculture plowing fields to remove milkweed as well as eliminating by herbicide is the actual cause.  This whole issue is explained here by Amber Sherwood-K and Jon Entine. The slide that suggested that a solution would be “Don’t eat GMOs,” was thus complete nonsense.

She also went astray in suggesting that the WHO had declared that glyphosate (Roundup) was carcinogenic. In fact this was done by the IARC, a subcommittee of the WHO and in doing so they ignored substantial evidence to the contrary, as described in this report in Scientific American. And they have also found caffeine, alcohol, sunlight, and the hairdressing profession in that same category.

Meanwhile the German Federal Institute for Risk Assessment completed a 4-year assessment for the EU, considering 150 new toxicological studies, all available existing toxicological studies (more than 300) and nearly 900 peer-reviewed publications, concluding that

the available data do not show carcinogenic or mutagenic properties of glyphosate nor that glyphosate is toxic to fertility, reproduction or embryonal/fetal development in laboratory animals.

Gardening advice

In the last part of her talk she suggested growing more local plants that would require less care and fertilizers that could run off. Some of particular interest were cardinal flowers, Joe Pye weed and Monarda (bee balm).

We found it surprising that in this talk she avoided mentioning any “chemicals” by name, and she told us this was because this was a layman’s talk. Without naming them, she mentioned that some were listed in her NY Times article. These were glyphosate, carbaryl, malathion and 2,4-D. Of these, glyphosate and 2,4-D are herbicides of very low and relatively low toxicity. Carbaryl (also called Sevin) and malathion are moderately toxic to humans (and carbaryl to bees), but are generally used only in small amounts in gardens and probably are not major runoff candidates. Glyphosate binds to the soil and is seldom found in runoff.

During her talk Lewis had a great deal of trouble pronouncing bacillus thuringiensis, which might indicate that she is uncomfortable pronouncing these chemical names and thus leaves them out of her talks.

Overall, as a chemist, I was not happy with her demonizing the entire class of “chemicals” as all bad without any specific science to back up her assertions. However, her heart is generally in the right place in wanting to reduce runoff from suburban lawns into our water supply. We haven’t treated our lawn with anything in years, so we are way ahead of her, perhaps primarily because we are lazy or cheap, but our lawn still looks fine when it rains enough.


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