GMO is not only a broad but a controversial subject as well. Generally the term is majorly used to refer to crop plants that have been genetically modified to be used for animal and human consumption (even though GMO technology has been used in pharmaceutical industry as well).
Genetic engineering allows selected individual genes to be transferred from one organism into another, even between non-related species in order to enhance desirable traits and improve nutritive value in some instances.
An example of a GMO is Bt. Corn. B.t. (Bacillus thuringiensis) is a naturally occurring bacterium that produces crystal proteins that are lethal to insect larvae. B.t. crystal protein genes have been transferred into corn, enabling the corn to produce its own pesticides against insects such as the European corn borer.
Potential human health impacts, including allergens, transfer of antibiotic resistance maker genes and other unknown effects e.g. congenital transfer of harmful genes to the unborn.
Potential environmental impacts, include unintended transfer of trans-genes through cross-pollination, unknown effects on other organisms (e.g., soil microbes), and loss of flora and fauna biodiversity.
Criteria used to asses risk status of GM foods:
Check for the presence of genes usually associated with allergic reactions.
Transfer of genes from GM foods into the body cells or bacteria in the GIT.
Movement of genes from GM crops into other conventional crops or related species. Mixing of genes would raise food safety issues.
Vary from country to country; some countries have strong policies e.g. the U.S.A and European countries while others have more relaxed or no policies at all (especially third world countries).
Kenya for instance legislated a law (Kenya gazette supplement no. 17 of 2012 legal notice no. 40). This law makes it mandatory for millers to label all GM foods.
It is impossible to design a B.t toxin that would only kill crop-damaging pests and remain harmless to all other species. Case study: toxicity of B.t corn pollen to monarch butterfly caterpillars.
Insects will develop resistance against B.t and other crops designed to produce their own toxins.
Detrimental when herbicide resistance genes are transferred to weeds, which would then become herbicide resistant as well. If out-crossing occurs in animals, it would result to situations like autoimmunity (where the immunity system acts against the cells/tissues of the organism).
The trans-genes may trigger allergic reactions in consumers. In Brazil, a proposal to incorporate a gene from Brazil nuts into soybeans was abandoned because of the fear of causing unexpected allergic reactions.
The trans-genes may cross the intestinal walls into the circulatory system. Once in the system it may cross the BBB especially in kids with underdeveloped BBB. Traces of toxic substances of GMO origin have been found in the blood of pregnant women and their foetuses.
B.T crops secrete toxins from their roots into the soil. Aquatic organisms may be endangered if they eat leaves from B.t and other GMO crops.
Embrace GM technology with a lot of caution. Governments should adopt non-partisan policies when dealing with GM technology and dedicate more funds to scientific research in this field.