In most studies the levels of alachlor detected were low, usually below one microgram per liter. This level is less than half of EPA's MCL of two micrograms per liter of water. In contrast, several studies have found alachlor breakdown products more frequently and at much higher levels than alachlor. These data and other studies suggest that while levels of alachlor are relatively low in water supplies, levels of some breakdown products may persist and be at much higher levels than alachlor. Breakdown products form when a chemical degrades and breaks down.
Some breakdown products bind tightly to the soil.
Other names for breakdown products are transformation products or degradation products. These breakdown products have been detected in water supplies, sometimes at levels higher than alachlor. Levels of alachlor breakdown products were not monitored in this study. A recent study conducted from October 1997 to March of 1999 by the Suffolk County Department of Health Services collected well water samples from areas on Long Island that were especially vulnerable to pesticide contamination. Of these 21 samples, ten had levels of alachlor that exceeded the EPA's MCL of two micrograms per liter for alachor.