Environmental impact of Cu and Zn in feeds

Copper and zinc are routinely used as additives in feed for livestock and aquaculture farming and thus it is inevitable that these metals will be released to the environment.

 

Under Regulation (EC) 1831/3003 (EC, 2003), in order to protect human health, animal health and the environment, feed additives should undergo a safety assessment through a Community procedure before being placed on the market, used or processed within the Community.

 

The environmental risks of Cu and Zn arising from aquaculture were assessed using simple exposure models recommended by EFSA.

 

Concentrations of Cu and Zn in marine sediments, arising from the use of feed additives in sea cage aquaculture, were 21.3 mg/kg and 182 mg/kg respectively.

 

Concentrations, estimated for different fish types farmed in raceways/ponds/tanks and recirculation systems, ranged from 12.1 – 12.5 µg/l for Zn and 1.13 – 2.96 µg/l for Cu.

 

For all fish species in the cage, raceway/pond/tank and recirculating systems, predicted concentrations were below predicted no effect concentrations (PNEC), indicating that the use of both metals in feed additives for fish poses an acceptable risk to the environment where these types of facility exist.

 

It is important to recognise that exposure concentrations used for this assessment are likely to be highly conservative.

 

A more complex modelling approach was used for assessing the risks of inputs of Cu and Zn from livestock treatments.

 

The assessment utilised the Intermediate Dynamic Model for Metals (IDMM) and soil/agriculture and water chemistry scenarios that were selected to represent the agri-environment conditions that are likely to be experienced across European Member States.

 

For copper, a risk of exceeding the soil PNEC was only found for the long term exposure simulations (50 years) for manure derived from piglet rearing, in seven scenarios. In only two of these scenarios is swine rearing locally significant.

 

Risks of exceeding the soil zinc PNEC were predicted at fewer sites than for copper, but the number of manure types whose continuous application presents a risk of exceedence was larger.

 

Risks of exceeding the freshwater PNECs were fewer than those for soil, particularly for copper where only one potential exceedence was identified.

 

In contrast, leaching of zinc in drainage and runoff was more pronounced in response to increasing manure application.

 

In the extreme case of an acidic sandy soil, the surface water PNEC was predicted to be exceeded after 10 years by the continuous application of any manure type.

 

Apart from this scenario, zinc concentrations in surface waters tended to be more sensitive to application rate in the runoff scenarios rather than the drainage scenarios, although this does not necessarily lead to potential risks within the considered timeframe.

 

Overall, the livestock evaluations indicated that environmental risks are acceptable at the current time but in the future risks could occur in some systems.

 

The systems most vulnerable to metal input in manure were clearly acid sandy soils, represented in the scenarios.

 

The distribution of these scenarios within Europe is largely in Flanders, the Netherlands, northwestern Germany and Denmark.

 

There is a clear need to better establish whether such soils are as sensitive to metal inputs as is predicted here, for example by field surveys of copper and zinc concentrations in drainflow from fields with known histories of metal input rates.

 

Since problems of high metal concentrations in drainflow and runoff, once established, would be difficult to remediate, it is important to proactively assess soil sensitivity before setting policy on manure application.

 

The project developed on the grant with reference number NP/EFSA/FEEDAP/2008/01. More detailed data can be found the full Report and Annex 1 and Annex 2