Some recent studies seem to suggest taking a new and more cautious look at plastic water bottles and frozen meal containers. A surge in research into plastics in food and water is raising questions about the accumulation of microplastics in the body. But the field is young and studies so far are limited. The World Health Organization report concluded two years ago that there was no clear risk to human health. But researchers only started measuring plastics in the human body — and trying to assess the health effects — in recent years.

Older adults without heart disease shouldn't take daily low-dose aspirin to prevent a first heart attack or stroke, an influential health guid…