INTRODUCTION TO THE MARINE ENVIRONMENT AND POLLUTION - Marine Pollution: What Everyone Needs to Know - page 6

being deposited into the ocean in precipitation and becoming
a water pollutant.
What are the major ways that land-based pollutants enter
the marine environment?
“Ocean dumping” refers to transporting materials in a barge
and physically dumping them in the ocean. The dumping of
industrial, nuclear, sewage, and many other types of waste
into oceans was legal in the United States until the early
1970s, when it became regulated; however, dumping still
occurs illegally everywhere. The movement to ban ocean
dumping of sewage sludge gained momentum in the United
States when contaminated wastes from sewage-derived
microorganisms were discovered at public beaches, along
with unsavory items such as hypodermic syringes and tam-
pon applicators. Most of the chemical pollution in the ocean
comes into the water through pipes rather than dumping.
While many pollutants are discharged (legally) from indus-
trial or residential areas, others come from agricultural areas.
Factories and sewage treatment plants release their wastes
into receiving waters through a pipe, referred to as a “point
source,” which can be monitored and regulated by environ-
mental protection agencies. Since passage of the Clean Water
Act in the United States in 1972, much progress has been
made in controlling pollution from point sources. Combined
sewer overflow (CSO) occurs in older cities, however, where
storm drains connect to pipes going to sewage treatment
plants from homes and industries. Heavy rainfall can over-
whelm the capacity of the sewage treatment plants, causing
everything to go out into the water untreated. The resulting
bacterial contamination from sewage leads to beach closures
for health reasons.
In recent decades attention has moved from point sources to
diffuse runoff and atmospheric deposition (called “nonpoint
sources”). Contaminants that wash into the water from soil,