St. Lawrence Cement, a subsidiary of the world’s second-biggest cement maker Holcim Ltd., must pay damages to neighbours of a Villeneuve, Quebec-based plant for the inconveniences its smoke and dust caused them.

The Supreme Court of Canada said today in a unanimous decision by six justices that the company has to pay even if it operated the plant from 1955 to 1997 using the best available equipment to reduce smoke and dust, because Quebec law doesn’t require neighbours to show the company was negligent.

Residents living around the plant, most of whom had built their homes before St. Lawrence Cement began operating there, complained that odors and cement dust prevented them from enjoying their yards, drying clothes outside and forced them to spend time and money cleaning and painting.

The civil liability "is consistent with general policy considerations, such as the objective of environmental protection and the application of the polluter-pay principle,’’ Justices Louis Lebel and Marie Deschamps wrote in the decision.

The neighbours who lived closest to the plant can claim C$5,500 (US$3,897) for the damages, with an additional C$150 a year for owners to cover for paint costs, according to the original Quebec Superior Court ruling.

"This precedent setting decision will require further review and detailed analysis by all potentially impacted Canadian companies, in order to better understand our obligations consequent to this ruling,’’ the St. Lawrence Cement said in a statement released after the decision. The company also acknowledged the inconvenience the plant caused to its neighbours.

The damages could amount to C$15m in total, according to Ecojustice Canada, a non-profit environmental law organization whose lawyers intervened in the case.

"Future environmental nuisance claims will be more easily proven under a no-fault regime, and polluters will have even more incentive to clean up their act to avoid being sued by their neighbours,’’ Will Amos, a lawyer with the group, said in an e- mailed statement.