[3] In the later 19th century, Zhenhai was protected from the sea by a dike about 3 miles (4.8 km) long, made of large blocks of hewn granite.

[1] Zhenhai has suffered severe long-term air pollution mainly emanating from the Ningbo Petro-Chemical Economic and Technical Development Zone built on its eastern coast.

In September, 2007, 400 tones of acrylonitrile leaked from the LG-Yongxing plant and polluted air and underground water around adjacent areas.

[4][5] In late April, 2012, three million bees died in an orchard in Xiepu Town next to the Petro-Chemical Zone because of pollutants discharged by a chemical plant.

[7] From May 16 to 17, 2002, residents in Zhenhai launched protests against environmental degradation caused by the chemical industry, blocking the district's traffic on its main streets.