Microplastics
are ubiquitous across ecosystems, yet the exposure
risk to humans is unresolved. Focusing on the American diet, we evaluated
the number of microplastic particles in commonly consumed foods in
relation to their recommended daily intake. The potential for microplastic
inhalation and how the source of drinking water may affect microplastic
consumption were also explored. Our analysis used 402 data points
from 26 studies, which represents over 3600 processed samples. Evaluating
approximately 15% of Americans’ caloric intake, we estimate
that annual microplastics consumption ranges from 39000 to 52000 particles
depending on age and sex. These estimates increase to 74000 and 121000
when inhalation is considered. Additionally, individuals who meet
their recommended water intake through only bottled sources may be
ingesting an additional 90000 microplastics annually, compared to
4000 microplastics for those who consume only tap water. These estimates
are subject to large amounts of variation; however, given methodological
and data limitations, these values are likely underestimates.
Shellfish aquaculture often uses large amounts of plastic equipment and has been suggested as a potential source of microplastic contamination in the marine environment. To determine the influence of shellfish aquaculture on microplastic concentrations in bivalves and their environment, we compared microplastic particle (MP) concentrations in Manila clams Venerupis philippinarum and Pacific oysters Crassostrea gigas grown on commercial shellfish beaches with those in individuals of the same species grown on nearby non-aquaculture beaches in 6 regions of coastal British Columbia, Canada. MP concentrations did not differ between shellfish aquaculture and non-aquaculture sites for either bivalve species, sediment, or water samples. Plastic presence differed by site and oysters on sites with many synthetic anti-predator nets contained significantly, yet marginally, more MPs than those on sites without (0.05 vs. 0.03 g -1 dry-tissue weight on average). However, analysis of suspected MPs using Fourier-transform infrared spectroscopy in dicated a predominance of fibres from textiles (including nylon and polyester), which are not typically used in shellfish aquaculture, suggesting that this may be caused by the larger average body weight of oysters grown at non-aquaculture sites rather than by the degradation of aquaculture infrastructure.
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