EPA proposes dioxin limit for biosolids spread on farmland

The US EPA is proposing a limit of 300 parts per trillion toxic equivalents for dioxins in biosolids that are recycled and applied to the land as fertiliser.

Facilities preparing biosolids – treated sewage sludge – for land application would also be required to follow new monitoring, record keeping and reporting requirements for dioxins in biosolids that are to be applied to agricultural land.

Risk assessment studies have indicated that the rule extra limits are not needed for dioxins in biosolids placed in surface disposal units or incinerated.

In February 1993, EPA set limits for metals, pathogens and total hydrocarbons for land application, surface disposal and incineration of biosolids.

Only biosolids that have been treated to meet federal and state standards can be approved for use as fertiliser. Local governments decide whether to recycle biosolids as a fertiliser, incinerate them, or dispose of them in landfills. Human exposure to dioxins – which are known carcinogens – is primarily through food and drink (see related story).

EPA will seek consultation for 60 days following publication of the proposed rule in the Federal Register.

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