Sediment is the material (mostly mud and sand) that accumulates at the bottom of a River. The main risk posed by sediment in the Lower Passaic is from dioxin that was produced at the former Diamond Shamrock plant in Newark. For years, this toxic byproduct from the manufacture of Agent Orange was dumped into the River and it has since been transported both up and down stream by river and tidal flow.
This dioxin has been deposited most heavily in the shallow areas and mud flats near the river banks, with lower contamination levels in the deeper channels. According to the Environmental Protection Agency (EPA), the primary human health risk from this dioxin comes from the consumption of fish, mainly Carp; that feed on material at the bottom of the river and are then consumed by fishermen. Advisories against consumption of fish from the Lower Passaic have been in place for some time, but some level of fish consumption continues.