Heavy Metals Network

Previously the Urban/Industrial Heavy Metals Network and Rural Heavy Metals Network

The Heavy Metals Network is currently managed and operated for the Environment Agency, on behalf of  Defra and the Devolved Administrations by the National Physical Laboratory, with deposition measurements subcontracted to UK CEH.

What is measured?

The network monitors the concentrations in air, and the deposition rates of a range of metallic elements at urban, industrial and rural sites. In 2014, the Urban & Industrial Heavy Metals Network and Rural Heavy Metals Network were combined into a single Heavy Metals Network comprising 24 monitoring sites. All stations (except Lough Navar) measure Arsenic (As), Cadmium (Cd), Chromium (Cr), Cobalt (Co), Copper (Cu), Iron (Fe), Manganese (Mn), Nickel (Ni), Lead (Pb), Selenium (Se), Vanadium (V) and Zinc (Zn) in the PM10 fraction of air.

Additionally, heavy metals in deposition are measured at 5 rural sites with mercury in deposition additionally measured at 4 of these stations.

What is the purpose of the network?

The purpose of the network is to provide evidence of the concentrations of heavy metals in air near industrial sources and areas of population. The Heavy Metals Network now forms the basis of the UK's compliance monitoring for:

  • The Air Quality Directive (2008/50/EC) which provides a Limit Value for lead concentration in air of 0.5 µg/m3, expressed as an annual mean.
  • The 4th Air Quality Daughter Directive (2004/107/EC), which sets target values for arsenic, cadmium and nickel in the PM10 particulate fraction of ambient air.

The 4th Daughter Directive also requires monitoring of mercury and of metals in deposition, although no limit or target values are set.

Measurements at rural stations are used to generate a rural concentration field for the mapping of concentrations of metals in the UK. Mapping is necessary to assess concentrations of metals across the UK at locations at which monitoring is not carried out. They also provide information on the processes which influence concentrations and deposition and enables assessment of any ecological risks which might arise from heavy metal deposition.

Historically, this network grew out of several separate long-term monitoring programmes, funded by the UK Government and latterly responding to specific needs of EC Directives in relation to toxic and industrial metals.

The network originally included: five urban multi-element monitoring sites providing measurements of nine important trace elements (Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn and V), eight sites for the monitoring of ambient lead resulting from lead in petrol (two rural, three urban and three kerbside) and eight sites operating in three industrial areas monitoring lead. A short-term survey from 2000-2001 at 30 industrial site locations across the UK established the UK's position with respect to the requirements of the 4th Daughter Directive which was then being drafted. Five of these sites continued to operate (PDF 509KB).

In 2003, all monitoring was rationalised into a single integrated network in order to unify methods and practices. In September 2004, the number of elements measured at the old Industrial Metals sites was increased to ensure consistency across the Network. In early 2011, two sites in Bristol were closed and two new sites in the Swansea Valley opened.

In early 2014 the Urban & Industrial Heavy Metals Network and Rural Heavy Metals Network were combined into a single Heavy Metals Network comprising a total of 24 monitoring sites. As part of the merging of the two networks eighteen stations were closed, nine from each original network.  

In 2016, the site at Harwell was closed and relocated to Chilbolton. During 2019, both Walsall Bilston Lane and Runcorn Weston Point were closed. A new site at Walsall Pleck Park was opened in January 2021, to replace Walsall Bilston Road.

During 2021 and 2022, all the ambient air samplers across the network were replaced with Digitel DPA-14 samplers.

How is the network run?

Sampling is now undertaken over one week periods at sites, of the PM10 fraction of particles using Digitel DPA-14 samplers. Analysis of samples occurs by Inductively coupled Plasma - Mass Spectrometry (ICP-MS) analysis, in accordance with European Standard EN 14902:2005 at a UKAS-accredited laboratory.

How to view data

You can view data for sites within this network using the links below:

View data for sites for Heavy Metals network

Use the dropdown list below to view data for a particular monitoring site.