B5. Pressure from pollution

B5b. Marine pollution


Type: Pressure indicator


Indicator Description

The indicator shows the combined input of six of the most hazardous substances to the UK marine environment.  The indicator is based on levels of five heavy metals (cadmium, mercury, copper, lead and zinc) and one organic compound (lindane).  Pollution in the marine environment from these six substances should decrease to levels that are non-detrimental by 2020.



The combined inputs of all six hazardous materials into marine environments have shown a long term decrease of 78% since 1990.  Inputs of five of these substances show decreases since 2010, however the input of cadmium has increased by 3% in the short term.


Figure B5bi.  Combined input of hazardous substances to the UK marine environment, as an index of estimated weight of substances per year, 1990 to 2015.

Figure B5bi. Combined input of hazardous substances to the UK marine environment, as an index of estimated weight of substances per year, 1990 to 2015.

Source: Defra Marine Strategy and Evidence Division, using data provided by: Environment Agency, Northern Ireland Environment Agency, Scottish Environmental Protection Agency.

Levels of all six substances declined over the period 1990 to 2015.  Mercury has declined by 90% since 1990, and inputs of two other substances (cadmium and lindane) have declined by over 80%.  Inputs of the remaining three hazardous substances (copper, lead and zinc) have also declined by over 60% since 1990.

In the short term, inputs of hazardous substances decreased by 12% from 2010 to 2015.  Inputs of five of these hazardous substances declined in the short term: lead had the highest percentage decrease (-33%), followed by lindane (-16%) and zinc (-15%), and then mercury (-3%) and copper (-2%).  The input of cadmium has increased by 3% increase since 2010.

Assessment of change in input of hazardous substances

Long term

Short term

Latest year

Combined input of hazardous substances

2010 indicator improving

2010 indicator improving

Decreased (2015)


Inputs into the marine environment are estimated from concentrations and flow rates in rivers entering the sea and those from estuarine and coastal point sources.  Riverine inputs reflect both point and diffuse sources upstream of the sampling point and tend to be strongly influenced by flow rates.  Flow rates are heavily affected by rainfall patterns so year to year fluctuations in pollutant loads are likely.

A detailed illustration of changing levels of each input is seen in Figure B5bii.  The low point in 2003 is thought to be a consequence of reduced river flows during an exceptionally dry year.  Conversely, levels of all six pollutants increased in 2012 and again in 2014 corresponding with years of heavy rainfall.  In 2012, England had the wettest year since records began in 1910; the summer was the wettest since 1912 increased rainfall in November and December contributed to extensive flooding.  In 2014, the winter (Jan – Feb) was the wettest since records began.


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Last updated: August 2017

Latest data available: 2015