Lawn treatments enhance the soil, kill off weeds, keep the grass well maintained and get rid of pests. Readily available commercial herbicides, pesticides and fertilizers let you see quick results. Depending on the quantities of the chemicals you apply--and their ingredients--you may find that they pose dangers to yourself or others. Keep an eye on your neighbor's lawn treatments as well; in some cases, the substances he chooses can make you ill.
Herbicides and Broadleaf Plants
Herbicides designed to eradicate dandelions and crabgrass may harm your ornamental flowers in the process. These herbicides target broadleaf flora but not grass plants. If wind, watering or the accidental application of the herbicide brings it in contact with broadleaf plants, these too will die off.
Pesticides and Cancer
Landscapers and homeowners use pesticides to kill off ant colonies, grubs and fleas. These insects generally do not harm your lawn. Instead, they are nuisance pests that make your yard difficult to enjoy. Their presence also decreases visual appeal, especially when ants build mounds..
The problem with pesticides is their toxicity not just to the target insects, but also to animals and humans. In 2002, then New York State Attorney General Elliot Spitzer warned that more than 95 percent of lawn pesticide ingredients are inert as opposed to active; these inert ingredients---which do not have to be listed on the label---consist primarily of toxins. This information prompted the New York State legislature to pass the New York State Pesticide Neighbor Notification Law.
Nitrogen Fertilizer and Groundwater
Depending on the acidity of your soil and its general makeup, having a healthy-looking lawn can depend on the addition of nitrogen-rich fertilizer. The University of Illinois' Extension Service estimates that an average lawn may need so much fertilizer that it introduces about a pound of nitrogen for each 1,000-square-foot area. Rainfall and watering cause nitrates to permeate the lawn's soil and eventually reach the groundwater; this increases nitrate levels in drinking water.
The Benton Franklin Health District warns that consumers cannot remove nitrate from water through common purification methods like boiling or filtering, and infants under six months of age are in danger of suffering---and in some cases dying---from methemoglobinemia (blue-baby syndrome).
Mowing your grass at an improper height is another lawn treatment danger. The ideal mowing height is considered between 2.4 and 3 inches. Homeowners may be tempted to cut the grass shorter to reduce the frequency of yard work, but this actually increases the care your lawn needs, since the grass and soil become more vulnerable to drought and insect damage. This in turn may cause you to increase the application of nitrogen-rich fertilizer and pesticides.