Government rules dictate that organic dairy farmers have to test for pesticide residues in their milk every year. OMSCo's farms are tested monthly, as an extra quality measure.
There are about 500 different pesticides licensed for use on non-organic dairy farms, ranging from aluminium-based slug pellets that kill hedgehogs and other wildlife, to organochloride seed dressings that stop insects and birds from feeding on the seed. Pests soon develop a resistance to these, so farmers using them must constantly change brands.
All pesticides have to be tested and approved by the government, which sets safety limits on their use. However, little is known about the so-called 'cocktail effect' of combining many different chemicals in the body. Pesticides have been linked to the disruption of our endocrine system and hormones. There is also evidence to link food allergies and chemical sensitivities in humans to a general over-exposure to chemicals. Even among experts there is disagreement about the risks. For example, in the United States, the herbicide cyanazine is being phased out as it is believed to be a cancer risk. In the UK, its use is unrestricted.