Previous tests have shown that these units -- which had been banned by the Supreme Court in 1994 -- can nullify the effect of 25,000 vehicles running on leaded petrol. Situated in no man's land between UP and Delhi in Mandoli village, the units' owners are cashing in on the ambiguity of the location. Even the local police are not sure about where one state ends and the other begins. A directive, when filed by the Delhi Pollution Control Committee (DPCC) to the local SDM, is most likely to become a shuttling document between the government offices of the two states.

Says R.P. Meena, SDM, Seemapuri: ``I am not aware of these units in my area. There have been no complaints. But if brought to my notice, I will take action.'' Local constables walk with easy familiarity in the area but protest that since this was UP, no action can be taken against the units.

The inconspicuous units have intimidating walls and 30-foot high chimneys that come alive at night. At the first sign of a strange car, guards who camp outside the locked doors of the units make sure that all lights are switched off and bolts in place. The names of the units and their owners are never disclosed. At around 11 pm, thick smoke spirals into the night sky from the chimneys. Workers toil quietly, pulling the waste from used batteries and shoving it with coal into the furnace. The molten lead is made into ingots for battery plates. These crude units operate on generator.

Each unit employs 10 to 15 labourers, mainly migrants from the neighbouring village from UP. ``We are paid Rs 1,500 per month. We have been hired by the contractor. We have not seen the owner,'' says a worker. Some of them were seen sleeping in between the stacks of batteries, lead plates and slag. The labourers work without gloves or masks, at times covering their faces with a cloth.

A study conducted in 1994 in Nangloi Mundka region had revealed a high concentration of lead in the soil: 72 to 2,062 microgram/kg against the normal level of 5 to 25 microgram/kg. The ambient air had lead content in the range of 3.1 to 7.9 microgram/cubic metre as against the permissible level of 0.37-0.67 microgram/cubic metre.

Last year, a few units were discovered in Shahbad Daulatpur, Karawal Nagar and now Seemapuri. ``The manufacturers can earn as much as Rs 5,000 every day. Being a very lucrative business, such units keep cropping up,'' says R.K. Goel, member secretary, DPCC. Last month, chance seizure of a truck laden with batteries had led to the discovery of units at Karawal Nagar.