1. Topic

2. Introduction

Quality assurance and control (QA/QC) is an essential part of any air monitoring system. It is a series of activities designed to ensure that air quality measurements meet defined and appropriate standards of quality, with a stated level of confidence. It should be emphasized that the function of QA/QC is not to achieve the highest possible data quality.

This is an unrealistic objective, which cannot be achieved under practical resource constraints. Rather, it is a set of activities enabling the network measurements to comply with the specific Data Quality Objectives (DQOs) for the monitoring programme. In other words, QA/QC should ensure that your data are fit for purpose.

Measured data of air pollution concentrations have a questionable value, unless the “quality” of each data point (in terms of its accuracy, representativeness) is known to a certain degree. This is fully understood and described in the EC AQ Directives. The Directives specify that the organisation(s) responsible for the quality of the data be named by the Member State (the National Reference Laboratory) and that Data Quality Objectives (DQOs) are specified for each compound.

In order to fulfil the data quality requirements, each network owner/operator has to specify and implement a system for controlling and assessing the data quality (a QA/QC system).

A set of procedures must be included which deals with the operations to obtain measured air quality data and also a system developed to ensure these operational procedures are followed.

When such a system is established and followed, it is possible to specify the accuracy and other quality characteristics of the reported data.

3. Discussion

Good data quality and high data capture rates are essential if the urban network is to achieve its objectives. To ensure comparability, consistent data quality assurance/control (QA/QC) procedures should be applied throughout the network.

Good QA/QC practice covers all aspects of network operation, including systems design and site selection, equipment evaluation, site operation, maintenance and calibration, data review and ratification. The successful implementation of each component of the QA/QC scheme is essential for the success of the program/system.

The Quality system that the responsible organisation has to set up can be described here in general terms. A number of reports and texts can be consulted which describes in full detail the specifics of the quality system (see the reading list below).

The main parts of the Quality System:

· Quality assurance: the management of the activities within the system, and setting of overall objectives and criteria.

· Quality control: the procedures of the day-by-day operations and data validation.

· Quality assessment: the external validation of the implementation of the quality system.

Quality assurance should consist of, for example:

· Setting Data Quality Objectives (DQOs), such as the desired accuracy of the data produced. The AQ Directives specifies required DQOs.

· Criteria for design of monitoring network and station location. The Directives have requirements related to this.

· Criteria for selection of instruments and monitors. The Directives specify the reference methods.

· Requirements to the competence and capacity of the Reference laboratory.

Quality control should consist of:

· Procedures for field operations, calibrations, maintenance etc.

Quality assessment should include

· Procedures for regular audits, inter-calibration exercises etc.

Basic description of data quality systems have been worked out by WMO, EEA and EMEP, see the reading list below for references. An example of a description of full Quality system developed to meet the requirements of the AQ Directives is also included (for Norway, in Norwegian).

The EU Air Quality Directives (http://www.europa.eu.int/comm/environment/air/ambient.htm) specify Data Quality Objectives (DQO) and certain data quality related requirements which should be used to guide the actual specification of QA/QC systems:

· DQOs: Requirements are set for minimum accuracy and data capture for monitoring data, as well as for modelled data and objective estimation;

· Location of monitoring stations;

· Minimum number of stations e.g. in urban networks;

· Reference monitoring methods.

The Commission organises EU wide or regional inter-laboratory comparison exercises (round robin tests, inter-laboratory exercises, spot checks in the monitoring networks) to ensure comparability of measurements at international level. The main organisation under the EC carrying out such activities is the "European Reference Laboratory of Air Pollution (ERLAP) of the EC's Joint Research Centre (JRC) Institute for Environment and Sustainability (IES), its Emissions and Health Unit: http://ies.jrc.cec.eu.int/Action_2112_-AQH.66.0.html

Another useful link is to the AQUILA network, the network of National Reference Laboratories in Europe, presently headed by JRC/ERLAP: http://ies.jrc.cec.eu.int/Units/eh/Projects/Aquila/

The QA/QC procedures of measurements must contain audits including control of the operation of monitoring equipment at the sites, maintenance and calibration in the laboratories and data control.

4. Recommendation / Conclusion

· Although the main principles of QA/QC system design apply to most network or instrumentation types, there are often characteristic differences in their emphasis and practical implementation. It is a common oversight to place too much emphasis on laboratory-based quality assurance activities, as these are often easier to control and monitor.

· Although such QA/QC tasks are vital, particularly for sampler-based measurement programmes involving substantial laboratory analysis, considerable emphasis in any network quality system needs to be focused on the point of measurement. Mistakes or problems at the start of the measurement chain cannot be readily corrected afterwards. Sample system design and maintenance, regular site visits, audits and inter-calibrations therefore play an important role in network quality assurance.

· Another unifying feature of network quality systems is the need for effective data screening and validation. In any measurement programme -however well designed or operated- equipment malfunction, human error, power failures, interference and a variety of other disturbances may result in the collection of spurious data. To maximize data integrity and utility, therefore, these must be identified and removed before a final, definitive dataset can be generated or used.

· The design of an effective and targeted QA/QC programme is only the first step in the process of quality management. The programme needs to be fully documented and compliance with its procedures and requirements actively monitored. Monitoring programmes often evolve over time as objectives, legislation, resources or air pollution problems change. Quality assurance programmes therefore also need to be regularly reviewed, to ensure that they remain properly targeted and fit for purpose.

5. Examples / Further Reading

AQ Data Quality Requirements, Bristol case

The Quality Assurance in Air Quality Monitoring in the Turku Region

Further Examples:

6. Additional Documents / Web Links

· EMEP QA/QC manuals etc: http://www.nilu.no/projects/ccc/qa/index.htm

· The EEA EUROAIRNET Criteria report, Chapter 4.5 on QA/QC: http://reports.eea.eu.int/TEC12/en

· Handbook on the Quality System for air pollution data for Norway. Report No. OR 55/2002, of Norwegian Institute for Air Research, Kjeller Norway (in Norwegian).

· CEN standards for measurement and monitoring methods: http://www.cenorm.be/cenorm/index.htm, click subsequently on standards and drafts/finding draft standards/domains/environment/air quality.

· Quenda – quality of environmental data. Uncertainty calculations – an overview http://www.fmi.fi/kuvat/EnteSneek.pdf

· Data, sources of information and useful web sites: Guidelines for Air Quality, WHO, 1999: http://www.who.int/environmental_information/Air/Guidelines/Chapter5.htm

· Technical guidance document: http://www.aeat.co.uk/netcen/airqual/reports/lsoman/lsoman.html

· Technical report No 11, Guidance report on preliminary assessment under EC Air Quality directives:http://reports.eea.eu.int/TEC11a/en/tab_content_RLR

· Technical guidance document: http://www.defra.gov.uk/environment/airquality/laqm/guidance/pdf/laqm-tg03.pdf

· Position papers on air pollutants: http://europa.eu.int/comm/environment/air/

· "European Reference Laboratory of Air Pollution (ERLAP) of the EC's Joint Research Centre (JRC) Institute for Environment and Sustainability (IES), its Emissions and Health Unit: http://ies.jrc.cec.eu.int/Action_2112_-_AQH.66.0.html

· Another useful link is to the AQUILA network, the network of National Reference Laboratories in Europe, presently headed by JRC/ERLAP: http://ies.jrc.cec.eu.int/Units/eh/Projects/Aquila/

Last Updated

25th January 2005