I read with concern that some companies continue to dump toxic substances into our sewers despite having been repeatedly fined in the past for similar offences (Recalcitrant printing firm fined for pollution; March 20).

Tat Seng Packaging Group had been caught four times before for polluting Singapore's sewers with toxic industrial used water.

But that did not stop the printing company from illegally discharging copper-tainted water yet again.

This blatant disregard for our water supply and public health so that companies can make a profit should not be taken lightly.

If just fining these companies does not work, the authorities should consider a six-figure fine for repeat offenders, and/or jail as well as caning for their bosses or chief executives.

Ronnie Lim Ah Bee