Sometimes the grass looks greener on the other side - even when it's not grass.

Witness school officials' rush, in New Jersey and other states, to carpet their athletic fields with a purported man-made improvement upon the old-fashioned plant. Readers of Frankenstein might have guessed where this was going.

In 2007, New Jersey officials found high levels of toxic lead while testing for contamination around a scrap-metal plant in Newark. But don't blame the factory. The source of the lead was a deteriorating AstroTurf field nearby. The disturbing discovery set off a series of field closures, along with investigations by local, state, and federal officials.

The Environmental Protection Agency's preliminary findings suggest the artificial-grass fields are safe, a spokesman told The Inquirer recently. Along with similar findings by the U.S. Consumer Product Safety Commission and New York state officials, that should give some comfort to the parents of children who have been using the fields. But it should not leave anyone feeling entirely comfortable with the whole Frankengrass experience.

There's still plenty of cause for concern about artificial turf. The Centers for Disease Control and Prevention has advised that children playing on it should take a number of precautions, including "aggressive" washing. New Jersey officials say children under 7 should stay off older turf. A few fake fields have been torn up and replaced. And legislators in New Jersey and New York have proposed moratoriums on the stuff.

Lead is highly toxic to the developing nervous systems of children. The amount considered harmful has steadily dropped over the years to the point that some experts now say no amount is safe.

Poisoning typically occurs through inhalation or ingestion of lead dust. The federal findings so far suggest that the lead in the athletic fields studied - unlike in the aging Newark surface - is safely contained in a form that won't enter children's bloodstreams through either of those routes. But every field can be expected to age and deteriorate at some point.

Given lead's well-known dangers to the turf-makers' target customers - children - their use of it was reckless and inexplicable. While lead is useful for pigmentation, it's not indispensable. American paint manufacturers, for instance, have managed to get by without it since a federal ban took effect three decades ago.

There are other unresolved worries about synthetic surfaces. The EPA has acknowledged that it's also looking into the safety of so-called rubber crumb made from recycled tires, which has become a popular base material for playgrounds and fields in recent years.

School and municipal officials should be readjusting their cost-benefit calculations before any more of them pay six or seven figures for a fake athletic field.

As the purveyors of artificial turf have often reminded us, you don't have to water it, mow it, or cancel games because it's muddy. But the mere possibility that it's poisonous is a monumental drawback compared with the alternative. Grass, anyone?