Unexpected Discovery of the Food Additive Nonivamide as a Main Estrogenic Contributor in the Three Gorges Reservoir

Thousands of natural and synthetic
substances in the
environment
have been reported to exhibit estrogenic effects. However, targeted
analysis of a limited number of typical estrogens or estrogenic candidates
is insufficient for key estrogenic driver identification since many
estrogenic substances are poorly characterized or even unknown. In
this study, chemometric methods were applied to link in vitro bioassays and nontarget analysis to identify key drivers of estrogenic
effects in complex environmental mixtures. The Three Gorges Reservoir
(TGR), which is located in the middle and upper Yangtze River and
provides drinking water to over 7 million people, was selected as
the study area. Sediment samples were collected during flood and nonflood
period to investigate toxic effects and chemical distribution. Bioassays,
including cytotoxicity tests and yeast two-hybrid tests, revealed
that samples collected during the flood period induced significantly
higher estrogenic effects than those from the nonflood period. Nontarget
screening by high resolution mass spectrometry (HRMS) detected 47,321
unique features, with 527 compounds being identified successfully
(level 2a). Chemometric analysis by correlation and weighted contribution
analysis indicated that N-[(4-hydroxy-3-methoxyphenyl)methyl]nonanamide
(nonivamide) was significantly positively correlated with estrogenic
activity (p < 0.05). Target analysis and the yeast
two-hybrid assay confirmed that nonivamide induced up to 25.2% of
the estrogenic effect of sediments at environmental concentrations.
This study is the first report on nonivamide occurrence in environments
and its unexpected estrogenic effects, highlighting its potential
ecological and health implications.