New Zealand’s $9.7 billion dairy export industry is reeling from the discovery of the toxic substance dicyandiamide (DCD) in milk. While present only in low levels, there is no international standard for acceptable levels in good products, and because DCD is toxic in high doses, shipments containing even the smallest traces of the substance could be rejected by those countries with zero tolerance policies for residues. What’s worse, melamine is a byproduct of DCD manufacturing and present in the chemical in small amounts, officials say.

Farmers apply DCD to their pastures to prevent nitrate, another fertilizer byproduct that can cause health problems, from running off into waterways. The trace levels were found in SMP, WMP and buttermilk powder made in September of last year.

Fonterra Cooperative Group broke the news by calling for a DCD suspension; New Zealand’s two largest fertilizer companies have suspended sales of DCD.