An acquaintance informed me, relating to the harmful effects various materials have upon his health and well-being, that it is 'artificial' substances that are the culprits. Clearly, in default of a real category difference, statistical studies of the kind envisaged would be ungrounded. The word 'nature' and its cognates can be defined by such statements as nature is the totality of what has existed, exists, can exist - always excepting one possibly existing entity, namely, a possible creator causing it all to be possible. We are part of nature and 'our nature' is the sum of our essential attributes. One of those attributes is the ability, and necessity, to make artifacts.
Some artifacts are 'more natural than others'.