At this point, biology and ecology are too poorly understood to be certain that question has been answered comprehensively. Risks must be assessed case by case as new applications of genetic engineering are introduced. In some circumstances, it is possible to assess risks with great confidence. For example, it is vanishingly unlikely that genetically engineered palm trees will thrive in the Arctic regardless of what genes have been added. But for many potential harms, the answers are far less certain.
Risk assessments can be complicated.
Because even rigorous assessments involve numerous assumptions and judgment calls, they are often controversial when they are used to support particular government decisions. For example, the approval of the first genetically engineered squash by the United States Department of Agriculture involved a controversial risk assessment. Under NEPA, risk assessments could lead to full-blown environmental impact statements, but so far all evaluations of engineered agricultural organisms have led to the legal conclusion that no environmental impact statement is needed. The public often has a brief opportunity to review and comment on the risk assessments. There is no standard set of questions that risk assessments must answer because of the great range of potential impacts of biotechnology products.