What is a primary concern regarding genetically modified organisms (GMO) as mentioned in the text?

The primary concern regarding genetically modified organisms (GMO) highlighted in the text is the insufficient evidence of their safety. This concern arises because while GMOs can offer potential benefits, such as increased crop yields and resistance to pests, the long-term impacts on health and the environment are still not fully understood. Critics often point to the need for more comprehensive studies and investigation into the consequences of consuming GMOs and their effects on biodiversity. Therefore, the ambiguity and ongoing debate about their safety is a central issue that influences public perception and regulatory discussions around GMOs.