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Update on Issue of Contaminated Soils in NZ

Owen McShane
Centre For Resource Mngmnt. Studies

An Update on Issue of Contaminated Soils in Rural and Urban Areas of New Zealand.

The Centre has received encouraging feedback on this issue.

Over the years I had noticed that many of the cases before the Courts involved claims of unlawful discharges to land, water and air.

It seems that what we read about is the tip of the iceberg because so many are settled out of court or withdrawn after long and expensive battles.

Many of these cases involve contamination by ‘heavy metals”.

The recent outcry over contaminated land seems to reflect the fact that the chemophobes who dominate so many councils departments have finally taken “a bridge too far”, possibly encouraged by their apparent freedom to impose bad science on individuals who have had neither the time nor the resources to fight back.

While these individual cases cost the economy large sums of money the much larger costs almost certainly lie with costs which are imposed on all contractors, land developers and homeowners even though these costs are the result of assumptions rather than sound science and sound cost benefit analysis.

For example, most readers will be familiar with the presumption that runoff from roads is highly contaminated and must be treated before the numerous contaminants find their way into the waterways or onto land.

Well, it turns out that the gunk we pump out of cesspits road sumps is has a lower level of heavy metals and other contaminants than ordinary soil.

A company with a contract to clean up city road sumps was charged by a Regional Council will unlawful discharges of the waste into a landfill on the grounds that such material was contaminated by heavy metals.

The company’s advisors asked for a list of the “heavy metals” which concerned the Council and after considerable delay were provided with a list of eight. They are listed below with their nutritional and toxicity status alongside:

Element Nutritional Status Daily Dosage

Chromium Nutrient, essential 50 – 200 µg

Nickel Nutrient Trace less than 150 µg

Copper Nutrient, essential 2 – 3 mg.

Zinc Nutrient, essential. 10 – 100 mg.

Arsenic Nutrient, trace. 12 – 25 µg.

Cadmium Nutrient, trace. Less than 70µg.

Mercury Toxic. None. Less than 100 µg.

Lead Toxic. None. Less than 20 µg.

Notice that of these eight ‘demonised” heavy metals only two – lead and mercury – are toxic.

The remainder, even arsenic, are essential to life and are a necessary part of our diet. Low sodium arsenic is correlated with central nervous system disorders, vascular disease and cancer. Zinc deficiency causes many problems including low sperm count, impotence, poor concentration, poor memory , and loss of appetite. Many people have been persuaded that chemicals are “bad” and seem convinced that the presence of ‘chemicals’ in the environment is necessarily bad for their health.

However, it is true that these metals can cause problems if they somehow achieve excessive levels in the body. Such poisonings are rare.

However, the Regional Council made two assumptions. The first was that roadside sumps would contain high levels of these heavy metals and that these levels would pose a threat to the environment.

So the company tested the contents of the typical road side sump. They found that the eight heavy metals in the material totaled only 21 parts per million. This is remarkable because it means that road run-off contains extremely low levels of these metals.

Ordinary soil will typically contain about 50 – 120 parts per million of copper alone, and about 50 parts per million of lead. Other typical ambient levels in rural soils are 20 ppm, for chromium, 20 ppm for nickel, 100 ppm for zinc, 8 ppm for arsenic, about 1ppm for cadmium, about 0.1 ppm for mercury.

The total for these eight metals in the sump sludge was only 21 ppm.

And yet the Puhoi motorway designers are being required to spend huge sums of money on large ponds and clean up systems to remove these metals from water which runs off the motorway surfaces. Similarly land developers are required to clean up the water which runs out of these roadside sumps. The costs of these systems runs into scores of thousands of dollars for quite small developments.

It seems we are removing contaminants which are already well below ambient levels in our soils. The even greater irony is that the New Zealand diet tends to be deficient in both zinc and copper and some extra “contamination” by these metals would probably do us good.

How many millions of dollars are we spending each year cleaning up materials and wastes which pose no threat to human or environmental health? Why are we doing so and who is providing the “science”.

The ARC has decided that unpainted zincalume roofs are no longer permitted because zinc is a contaminant. This is based on an estuarine study which showed higher levels of zinc in mud near to industrial zones but did not demonstrate any toxic effects on fish life, which is the claimed reason for the ban.

I have read many papers which document the “high” levels of contaminants, including “heavy metals” in water run-off from roads and roofs in New Zealand. All appear to simply assume that this high level in the run-off water will translate into high levels in soil or mud.

But the sludge from the road side sumps shows no such transfer from water to sludge.

Our soils remain deficient in copper and zinc.

So what is the problem? Surely before we impose these costs on homeowners we should be sure that there are some benefits at the other end.

It seems we are being ruled by chemophobes.


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