In the same way that polluted water can be deceptively clear, polluted soil can just look like plain old dirt. Given the contaminants that can be left behind by gas plants, oil refineries and other industries, however, it's very important to check that the soil in an area isn't toxic, before building houses or growing crops there. Presently, soil samples have to be sent off to laboratories, where processing can take up to two weeks. British entrepreneur Ed Bell, however, has invented a briefcase-sized soil-testing unit that can be carried into the field, where it provides results within minutes.

The device, known as the Safe Soil Tester (SST), was developed by a team of six at Bell's company, Crown Bio Technology Ltd, UK. In its present incarnation, the system tests specifically for one of the most common ground pollutants, carcinogenic polyaromatic hydrocarbons (PAHs).

The SST mixes soil samples with naturally bioluminescent vibrio fischeri bacteria. If PAHs are present in the sample, the bacteria will die, and their bioluminescence will cease. The device picks up this change in luminescence, and uses it to rate the toxicity of the soil. Each test takes only 12 to 15 minutes, and is reportedly better able to detect PAHs than traditional chemical testing.

Because it is GPS-enabled, the SST can then indicate the location of the polluted soil on a satellite map of the area.

UK Power Networks has already purchased some of the devices, for monitoring its own oil clean-up efforts at its numerous electricity transmission sites across England. Bell is currently negotiating with military and governmental partners in Europe, the U.S., Canada, Brazil and the Middle East, to develop SSTs that could test for pollutants such as heavy metals, radioactive materials, and disease pathogens.

In its present form, the SST sells for GBP 15,000 (US$24,062), with the bacteria costing an additional GBP 45 ($72). That initial price is said to be offset by the money saved on lab testing, however, and with the speed at which projects can proceed.