Week of 7/6/2008

Dear EarthTalk: What green-friendly lawn and garden pesticides are available today? I’m particularly interested in options that won’t harm my cats.

—Nancy Blanchard, via e-mail

Pesticides have greatly boosted agricultural yields over the last half century, so it is no wonder, given the commercial availability of many of these synthetic chemicals, that American homeowners apply 100 million pounds of the stuff each year to make their own gardens grow bigger and faster, too.

But the downside of using such chemicals is that they can poison people and pets as well as backyard wildlife: "Common insecticide ingredients such as 2,4-dichlorophenoxyacetic acid (2,4-D), atrazine and dicamba have been shown to harm mouse embryos at times equivalent to the first week after conception in humans," says Erica Glasener of The Green Guide. Due to such revelations, home gardeners are fast discovering the benefits of avoiding chemicals in favor of natural, less toxic alternatives.

But before thinking about applying pesticides, gardeners can design (or re-design) their gardens to make the most of native plants that have evolved over eons to thrive in local conditions without synthetic aid or lots of water. Choosing native plants appropriate to your elevation, soil type, drainage and sun exposure will naturally repel many common pests and also reduce the propagation of invasive exotic species.

Synthetic lawn and garden chemicals can poison people and pets alike. American homeowners apply some 100 million pounds of the stuff each year, but are fast discovering the benefits of using more natural and less toxic approaches.© Getty Images

Similarly, embedding your plants in healthy soil replete with beneficial insects and worms can also help reduce the need for pesticides. Laura Moran of Mainstreet.com suggests that home gardeners compost their vegetable food waste—which is chock full of nutrients that plants love—and mix it into existing soil to give the garden a healthy boost. "Aside from stimulating healthy root development," she writes, "the addition of rich compost also improves soil texture, aeration and water retention." It also provides a nice home, she says, for the beneficial bugs that are destroyed along with the bad ones by chemical pesticides.

If pesticides are necessary, there are a handful of organic varieties available. Bacillus thuringiensis ("Bt") is a naturally occurring bacterium that is lethal to most leaf-eating caterpillars on trees, shrubs, flowers and vegetables. According to gardening writer Jeff Ball, it is harmless to all other insects, animals and humans. It comes in a powder form for use as a dust, or, when diluted with water, as a spray. Organic chemists have formulated varieties of Bt to kill mosquitoes or potato beetles as well.

To control slugs in an environmentally friendly manner, The Green Guide‘s Glasener suggests recycling the black cell packs that vegetables and annuals are sold in, and placing them (empty) upside down near the base of plants. "Each morning, check the containers for pests, and if you find any, simply throw the container away with the pests inside," she says. Another easy slug control method is to use hollowed out grapefruit rinds in a similar manner around the base of plants, disposing of them if they turn up any slugs.

Pet owners may already be familiar with insecticidal soaps used to control fleas. Some of these soaps can also be used in the garden to repel insects. For more information, consult a local nursery specializing in organic methods and native plants. Find one near you via the free online Native Plants Nursery Directory.

CONTACTS: The Green Guide; MainStreet.com; Native Plants Nursery Directory

Dear EarthTalk: What’s going on with all the cases of autism cropping up and no one seems to know why? It stands to reason it must be something (or some things) environmental, yet every study allegedly turns up no conclusion? What are the possible causes?

—Jessica W., Austin, TX

Autism affects one in every 150 children born today in the U.S., up from one in 500 as recently as just 10 years ago.© jbcurio, courtesy Flickr

No doubt about it, autism rates have skyrocketed in the U.S. and beyond in recent years. According to the Centers for Disease Control and Prevention, the disease affects one in every 150 children born today in the U.S., up from one in 500 as recently as just 10 years ago. It’s become the fastest-growing developmental disability—more prevalent than childhood cancer, juvenile diabetes and pediatric AIDS combined—and it continues to grow at a rate of 10 to 17 percent per year.

While researchers think there is a genetic component to autism, they also believe environmental factors are playing a role in its recent increase. Environmental mercury and other heavy metal exposure, contaminated water, pesticides, a greater reliance on antibiotics—and even extensive television viewing by very young children—may be factors in mounting autism rates. Researchers at the American Academy of Pediatrics and other institutes have also identified flame retardants as possible culprits.

Vaccines containing the mercury preservative thimerosal (now mostly removed from the market) have long been blamed for causing autism, but scientific links are inconclusive. In lieu of a smoking gun, a more complex picture of autism’s environmental causes is now emerging.

Some researchers are focusing on the role of food in a young child’s development. Many autistic children suffer from digestive diseases or have genetic dispositions rendering them unable to naturally rid their bodies of toxins. As such, exposure to heavy metals, pesticides, contaminated water and even processed food could have a devastating cumulative effect, some researchers think. According to Brian MacFabe, a researcher at the University of Western Ontario who has studied autism triggers in rats, simple changes such as removing wheat and dairy from the diet could potentially bring about improvements.

Groups such as the nonprofit Healthy Child Healthy World say it’s about time researchers are looking at environmental factors. "Whatever triggered this current autism epidemic…autistic kids clearly need extra protection from further environmental assault," the group writes on its blog. They advise parents to be vigilant about the industrial cleaners used in school buildings and the pesticides sprayed on playing fields, where kids spend 25 to 30 hours per week. They and other groups are also looking at the role of untested chemicals in common cleaning products: phthalates, glycol ethers and other known toxins.

Others wonder if a collective "nature deficit disorder" among children plays a factor in rising autism rates. Outdoor exposure has long been associated with healthier cognitive functioning in children, with reduction in Attention Deficit Disorder symptoms and greater emotional capacity. But new findings suggest it could impact autism, too. Last year, Cornell University researchers found higher rates of autism in counties where more households subscribed to cable and children under the age of three regularly watched TV. The Amish, with almost no exposure to TV, have little evidence of autism, notes the study.

CONTACTS: CDC Autism Information Center; Healthy Child Healthy World