Septic tank and drain field microorganisms have very limited capability for catabolizing petroleum products and chlorinated solvents, and cannot remove dissolved metals; although some may be absorbed into septic tank sludge or drain field soils, and concentrations may be diluted by other groundwater in the vicinity of the drain field. Cleaning formulations may reduce drain field efficiency. Laundry bleach may slow or stop microbial activity in the drain field, and sanitizing or deodorizing chemicals may have similar effects. Detergents, solvents, and drain cleaners may transport emulsified, saponified or dissolved fats into the drain field before they can be catabolized into short-chain organic acids in the septic tank scum layer.