Because a small amount of chemicals on the land can be gradually broken down to the point where they cannot be detected, it isn't a given that no chemicals were sprayed over the course of the vegetables 'life cycle.
因為少量的化學農藥在蔬果內會逐漸被分解，檢驗不出來，不表示栽植過程沒有噴灑過農藥。