Why trash a suitcase just because it has become scuffed up? It can still do its job. Or if your ax handle breaks, attach the head to a new handle and go on chopping wood. The age-old impulse to reuse possessions is an essential component of sustainable behavior, but it is worth thinking twice when doing so.

Tarryn Pitt of Oregon demonstrates the virtue of careful reuse. For her wedding celebration this May, Tarryn is thrifting the needed objects rather than investing in new ones. Among the items she has acquired so far are hundreds of second-hand dessert plates, dinner plates and goblets, as well as lace tablecloths, doilies, candlestick holders and so on. Realizing that the decoration on old ceramic plates might contain lead, she has tested them. Knowing her plates are lead-free, Tarryn can be confident that her thrifty approach is also a healthy one.

One should apply similar care whenever using an item again and again, particularly if made of plastic. For instance, plastic water bottles, including those intended for reuse, can leach chemicals into their liquid contents. Bottles made of polyethylene terephthalate, identified on the container by the numeral 1 inside a triangle, may contain the contaminant antimony. Bottles labeled with a 7 are formed from any sort of plastic not classified as types 1-6; these may contain bisphenol A, a chemical known to pose significant health risks. Given the known phenomenon of plastic leaching, try to avoid reusing single-use bottles as well as any bottle not labeled “BPA free.”

Likewise, think twice before reusing plastic eating utensils and takeout containers. You might avoid letting food come into contact with any plastic, which sheds microplastics as it ages — but definitely avoid black plastic. This material commonly originates as recycled e-waste, so products made with it could contain the flame retardants with which television and computer housing are typically treated. Because leaching from black plastic poses serious health risks, never reuse items made from this material — and why not avoid it altogether by eating with metal utensils and choosing not to order takeout served in black plastic containers?

A sustainable lifestyle should certainly include reusing possessions. But like Tarryn Pitt, let’s do so thoughtfully — our health could depend on it.

David Conwell is a former history teacher who belongs to Brunswick’s Sustainability Committee and the nationwide advocacy organization Citizens Climate Lobby.