accumulates

TFA is what's known as a "forever chemical" which means that it breaks down extremely slowly in nature, and so accumulates over time.

If Mars was "warm and wet," he continued, valley heads could be seen anywhere where rain accumulates.

“Ill fares the land, to hastening ills a prey, Where wealth accumulates, and men decay,” warned the Anglo-Irish poet and novelist Oliver Goldsmith in 1777.

The bloom currently wreaking havoc off the coast produces a neurotoxin called domoic acid, which accumulates in small fish like sardines and anchovies.

Domoic acid is a neurotoxin produced by harmful algal blooms that accumulates in filter-feeding fish — including anchovies and sardines — which are then eaten by seals, sea lions and dolphins.