TOXIC CLEANUP

Genetically engineered bacteria that eat hydrocarbons and thus could clean up oil spills have been known for some time; they were the first to be subject of a US patent [AtE Aug 80]. Other en-gineered bacteria have been reported on earlier, e.g., Frostban and Ice Minus to make strawberries frost-resistant [AtE Jun 87] and fungi that eat coal to excrete methane gas [AtE Nov 87].

In all of these cases the bacteria have been engineered in the lab and then carried into the field. But for clean-up of toxic wastes, a new way is being investigated: supporting the bacteria already on site and making them multiply. For example, there are the town gas sites, a relic from the gaslight era. Municipal gas works used to make their own gas for local consumption all over the US; in the East by heating coal with steam, in the West by thermal cracking of petroleum. The residues left behind by both of these processes were simply buried, and though they contained toxic chemicals, they have not given any trouble; to the contrary, they proved a great boon to the contemporary "what if' warriors who fear for the health of all when we burrow underground like moles and ingest some of these substances. One group of toxic carcinogens among them are polycyclic aromatic hydrocarbons (PAH), well known for their presence as a combustion product in coal-fired power plants. Here they come straight out of the stack to enter the atmos-phere and occasionally people's lungs, but since when have the sham-environmentalists cared about the environment? There are billions in the Superfund for toxic cleanup, and the pressing prob-lem today is not to provide abundant energy, but to spend up to $300 million per town gas site to clean up the residues which threaten nobody.

Anyway, the cleanup can probably be made substantially cheaper by using bacteria to break down the PAHs and other toxic substances into harmless compounds. The way this is planned to be done is by several methods of encouraging growth (that is, split-ting and thus multiplying) of those bacteria that are already present and are known to cause the desired breakdown. At present the most effective way is bioremediation, the shotgun ap-proach of increasing all bacteria by plowing the soil to increase aeration, then spraying it with water containing nutrients. Alterna-tively, the "genetic ecology" approach takes a sample of the soil and investigates which environmental factors will make the desired toxin-eating bacterium thrive, and these factors are then reproduced in the field. Only if these two methods fail would it be necessary to engineer specific bacteria for the job.