> Rather than introduce just the number of particles released by one container, the researchers instead exposed the cells to particle concentrations that infants and toddlers might accumulate over days or from multiple sources. > After two days, just 23% of kidney cells exposed to the highest concentrations had managed to survive So they used concentrations that they believe toddlers might accumulate over two days an…
> Exposure modeling results suggested that the highest estimated daily intake was 20.3 ng/kg·day for infants drinking microwaved water and 22.1 ng/kg·day for toddlers consuming microwaved dairy products from polypropylene containers.
> Furthermore, an in vitro study conducted to assess the cell viability showed that the extracted microplastics and nanoplastics released from the plastic container can cause the death of 76.70 and 77.18% of human embryonic kidney cells (HEK293T) at 1000 μg/mL concentration after exposure of 48 and 72 h, respectively.
If I'm reading this right, they exposed these HEK293T kidney cells to far higher concentrations (1000 μg is 1000000 ng, and that's per mL) than toddlers would be exposed to from these containers. So the fact that the cells die doesn't really mean much, since exposure to too much of anything will cause cells to die.
The real question is whether the exposure you'd receive from occasional microwaving would be enough to ever cause any meaningful health problems. Unfortunately papers like these always like to talk about dramatic metrics like 'billions of nanoplastics' without putting that into any meaningful context.