Organic farming is an approach to farming in which synthetic chemical insecticides and herbicides and inorganic fertilisers are excluded. Underpinning organic farming is the idea that farming should rely on ecological processes, biodiversity, and cycles adapted to local conditions, rather than the use of inputs with adverse effects (e.g. agrochemicals such as pesticides and synthetic fertilisers).

Organic certification is protected by law, and certification bodies (e.g. the Soil Association in the United Kingdom) specify the practices, methods of pest control, soil amendments, and so forth that are permissible if products are to achieve organic certification. In the UK, for example, food can only be labelled as 'organic' if production rules are met; at least 95% of the agricultural ingredients are organic; and the product, its labels and suppliers are certified by a Defra-approved organic control body.

Overnutrition generally refers to excessive intake of energy and sometimes to the excessive intake of a particular macronutrient or micronutrient. Overnutrition in terms of energy often results in being overweight or obese.

Ozone is a molecule consisting of three oxygen atoms (chemical formula O₃; ‘trioxygen’). In the upper atmosphere (‘stratosphere’) ozone plays an important role in absorbing ultraviolet radiation from the sun, but is also a greenhouse gas, and at the surface has negative impacts on human health and plant growth. Ozone is also one of the by-products from atmospheric methane oxidation.

Ozone layer depletion is a decline in the level of ozone gas (O₃) present in the earth's stratosphere, owing to its breakdown into oxygen (O₂). This breakdown can be affected by natural processes, but is known to have been accelerated by the release of man-made chemicals, such as refrigerant gases. The ozone layer acts to reduce the amount of light at ultra-violet wavelengths reaching the earth's surface; wavelengths that can have harmful impacts on humans, including skin cancer.