Context:
Third, Séralini and his fellow travelers ignore the ancient adage that the dose
makes the makes the poison. It has been known since Paracelsus made the observation in the 16th century that all things can be poisonous but the dose determines whether or not they are harmful. Without expressing it in those terms, we all know it to be true for substances as disparate as carbon monoxide and Tylenol.
More:
http://www.forbes.com/sites/henrymiller/2012/02/22/the-science-of-things-that-arent-so/2/