So, exactly what is our farming community - from farmer to factory to federation - doing about identifying such sites, checking for problems, and testing the products grown on and around them and which consumers eat?
Given the flippant "she'll be right" reaction to the landfarm question, the answer is likely to be diddly-squat.
Which would be no surprise, because if they were created by previous generations chances are most farmers don't know where half their dumps are located, let alone what's in them.
Considering the sheep-dipping and gorse-spraying programmes, and the DDT, PCBs, 245-T and other dioxins and carcinogenic nasties farmers have employed over the years, the potential scale of the problem is vast.
Sure, there are now some decent collection and recycling efforts under way to clean up hazardous agricultural waste as it occurs, but there weren't in the past; what was left over or worn out simply got buried. And forgotten.
Yes, there is routine random testing of product, both here and when our goods arrive overseas, but it's a hit-or-miss approach that won't necessarily identify a problem. Cold comfort any contaminants older dumps have leached into the food supply have probably been ingested already.
See, the crucial issue is what impact finding toxins in milk or meat would now have on our markets. Which is why the industry's feigned blindness to this possibility is so baffling.
Surely unless it can demonstrate conclusively - and continuously - that there is no problem, Fonterra must cease sourcing milk from all landfarms, for starters. If that means a farmer's deal to accept drilling waste to create more useable acreage might not be so lucrative, tough.
However the Feds motto seems to be "it's 100 per cent pure so long as you don't look too closely".
Certainly that attitude drives intensification and is behind support for Hawke's Bay allowing an increase of up to 250 per cent of nitrates into the Tukituki River in order to facilitate dairying within the Ruataniwha irrigation plan.
Equally, behind objections to Horizons Regional Council's "One Plan" which (in a first in New Zealand) aims to actively regulate landuse in direct proportion to environmental impacts.
On these topics, if you're in Waipukurau on Monday evening drop in to the primary school at 7.30 to hear Dr Mike Joy of Massey University presenting "The truth about dairy intensification."
Taranaki's oil-soaked pastures are pointing up what's wrong with our rush to intensify; progressive councils like Horizons and experts like Dr Joy aim to elaborate how it can be done sustainably.
Attendance should be compulsory for Fonterra and Federated Farmers.
That's the right of it.
Bruce Bisset is a freelance writer and poet.