Marin County

• In November 2004, Marin County, California, became the first county in the United States to ban the cultivation of GMO crops in its jurisdiction. The measure was passed with 61 percent in favor. The main reasons for the measure include concern for the local environment, the health of the local population, the ability of farmers to save their own seed and for the potential of uncontrolled hybridization of GMO crops.
  
  

Organic Farmers

• In addition to environment and health, organic farmers are especially concerned about GMO crops because these organisms are a threat to their livelihood. These organisms are under copyright as intellectual property by the corporations that create them, and can pollute organic fields by hybridizing with the organic crops. This effectively makes that farmer's crops not organic because they are crossbred with GMOs. It has been upheld in Canada that when this happens, the organic farmer is liable for damages to the company who created the crop because it constitutes a theft, even if the farmer had no control over the encroachment.
  
  

Consumer Groups

• Consumer groups worldwide have pushed for mandatory labeling of GMO foods. The main concerns are that without labeling consumers cannot make informed dietary choices. They have no way of knowing whether something they are buying contains GMO products, and thus no choice in whether they are supporting something ethically contentious. GMO products have caused allergic reactions in some people, and it is still unknown what the long-term effects on nutrition and health might be. People cannot know whether they are putting themselves in harm's way unless they are informed of the contents of their food.
  
  

Scientists

• Many scientists have concerns about GMOs on the basis that there is currently no way to accurately test the effects of the introduction of new gene combinations into the environment, and it is unknown what, if any, deleterious environmental effects there might be. In 2000 a group of more than 800 scientists submitted a letter to the United Nations and World Trade Organization outlining their concerns and advocating for the ban of GMOs until further testing could be done. Beyond the numerous potential environmental hazards, these concerns include the further monopolization of agricultural food system by a few large corporations.