Are organic substances like fertilisers and pesticides allowed?
Pesticides are commonly used in organic farming, although this should only include organic-approved substances derived from natural sources rather than synthetic substances.
In the European Union, organic farmers are required to use organic, natural or naturally derived substances and low-solubility mineral fertilisers (which reduce overuse of fertilisers and pollution from intensive farming), in accordance with the list of approved organic pesticides.
In the USA, the use of organic treatment is well-regulated, and biological, botanical or mineral inputs can be applied to prevent or control crop pests, weeds and diseases while ensuring their use is documented in an organic system plan. Permitted treatment includes crop nutrient or soil supplementation, although soil deficiencies must be tested and documented, to ensure that fertilisers are necessary and to avoid pollution from micronutrients made from nitrates or chlorides, which are not allowed. For fertilisers, mined substances of low or high solubility can be used, provided that the substance is not prohibited.
Are organic substances effectively safety tested?
The European Union (EU) has authorised a number of natural pesticides commonly used in organic farming prior to the European Food Safety Authority’s approval, despite the threat posed by the exposure to a cumulative mixture of harmful substances. In the EU, no chemical associations or interactions are assessed as part of the natural substance safety testing.
In comparison, the USA has a more robust pesticide risk assessment process. Both organic and synthetic pesticides approved for use on conventional and organic crops undergo the exact same scientific evaluation by the Environmental Protection Agency (EPA). Most organic pesticides used in the USA are naturally derived from plants, microorganisms or other natural sources, and are therefore exempt from the requirement of a documented tolerance level. Nevertheless, the EPA still evaluates scientific data on all pesticides to ensure that, when used according to label directions, the product will not harm people, non-target species or the environment. Recent guidelines have also been established for assessing the cumulative risk from pesticides with similar mechanisms of action, evaluating the potential for exposure to more than one pesticide at a time (but only considering groups of substances that share a common mechanism of toxicity), approximating actual exposure and potential risk from food, drinking water and domestic sources.
Non-organic synthetic chemicals in organic crops
In the EU, if organic measures for plant protection (such as fertilisers, soil conditioners and cleaning or disinfection substances) do not exist or are not available, chemically synthesised inputs are allowed, although these are ‘strictly controlled and verifiable at annual inspection’, according to the Department for Environment Food & Rural Affairs (Defra) of the UK. While the use of synthetic substances is only approved under exceptional conditions and with the permission of the relevant competent authority, there are no published general guidelines available detailing what these exceptional conditions include, and when asked, Defra representatives were unable to provide a general comment.
In the USA, 25 synthetic chemical substances are approved for organic crop pest control, where organic alternatives are not commercially available or prove insufficient to prevent or control pests. The substance to be used must be approved and included in the national list of allowed substances, and there must be an agreement between the farmer and their certifying body that the treatment is acceptable, with sufficient control measures in place to avoid food contamination.
In both the EU and USA, the use of synthetic chemical-treated seeds and starter stocks is permitted for most crops, if no organic alternative is available.,  US regulations also stipulate that these crops must have been organically maintained for a minimum of one year before being sold with an ‘organic’ label.
Processing and treatment of organic crops
In EU organics regulations, there are only vague definitions of pre- and post-harvest treatment, stating that it should only serve as ‘plant protection’ measures. In the USA, pre- or post-harvest treatment such as desiccation is allowed in organic farming, if organic methods are insufficient to prevent or control pests, weeds or diseases. Practices such as ionising radiation are prohibited in organic production in both the USA and the EU, but other than this, details of approved processing and pre- or post-harvest treatment is not clearly defined or specified., 
Are effective land management measures in place to stop contamination of organic farms?
The contamination of organic crops with harmful non-organic pesticides is a major problem worldwide. In the European Food Safety Authority’s 2015 annual report on pesticide residues in food in the European Union (EU), data highlight that ‘overall, 97.2% of the sample analyzed fell within legal limits, i.e. the measured levels did not exceed the maximum residue levels (MRLs) permitted in the EU; 53.3% of the samples tested were free of quantifiable residues (residue levels below the limit of quantification, LOQ) while 43.9% of the samples contained quantified residues not exceeding the MRLs. In 2.8% of the samples, the residue levels exceed the MRLs. Taking into account the measurement uncertainty, 1.6% of the samples clearly exceeded these legal limits (non-compliance) triggering administrative actions by competent authorities.’ While pesticide testing in organic products accounts for 6.3% of all products tested, 140 different pesticide residues were quantified in organic produce in concentrations at or above the LOQ. Aiming to tackle this situation, the EU imposes a three-year minimum period with buffer zones confirmed by annual inspection and testing regime.
In the USA, this problem is even more marked, as the use of synthetic pesticides and herbicides in conventional farming is less restricted than in Europe; over 900 synthetic pesticides, including substances like acephate and paraquat, which have been banned in the EU, are still approved for use in conventional farming in the USA. In an attempt to combat this, US regulations state that organic farms must have distinct, defined boundaries and buffer zones, with run-off diversions to protect organic fields and soil testing requirements helping to ensure organic crops are not grown in contaminated soils.