Air quality

Review and Assessment of Carbon Monoxide

Information about air quality in solihull

5 Review and Assessment of Carbon Monoxide

5.1 The Government has adopted an 8-hour running mean

of 11.6mg/m³ (10ppm) as an air quality standard for carbon monoxide (CO), with an objective of meeting that standard, as the maximum 8-hour running mean, by the end of 2003. Given an averaging period of eight hours, the focus of the review and assessment should be on non-occupational exposures at near ground level locations, including:-

• Background locations,
• Roadside locations, such as on pavements or close to the facades of buildings,
• Other locations where people may be exposed regularly, such as schools or hospitals.

5.2 Carbon monoxide

is a gas that is formed by the incomplete combustion of fuels that contain carbon. As a rule, the less efficient the combustion, the higher the levels of carbon monoxide produced. Prolonged exposure to very high levels of carbon monoxide can result in death. At lower concentrations the risk of heart problems increases in predisposed individuals due to the reduction in the oxygen-carrying capacity of the blood. The biggest danger from carbon monoxide is in the home and arises from faulty combustion appliances, which can release the gas in sufficient concentrations to cause death. In the outdoor environment concentrations can still increase to levels high enough to cause adverse effects on health.

5.3 The main source of carbon monoxide

in the West Midlands is now road traffic, in particular petrol-engined vehicles, which accounts for over 95% of its emissions. Industrial sources are thought to account for less than 1% of the emissions, commercial and residential sources for another 1%, and the balance from miscellaneous sources (Figure 5.1)

5.4 National policies

have already reduced the emissions of carbon monoxide from motor vehicles. Those emissions are expected to fall by 50% between 1996 and 2006, despite an estimated increase in traffic, of between 13.5 to 14.5%, in the West Midlands (Local Transport Plan 2000).

5.5 Industrial emissions

account for only a small proportion of the total emissions of carbon monoxide. However, those emissions may represent a significant proportion of the emissions, near to particular industrial premises. In Solihull, only one industrial premises has been identified as potential emitter of carbon monoxide:-

• a combustion process.

This process is authorised under Part 1A of the Environmental Protection Act 1990 for Integrated Pollution Control (IPC).

Sources of Carbon Monoxide in the West Midlands

Figure 5.1

5.6 Carbon Monoxide Levels in 1999.

Air pollution is measured at a number of locations across the West Midlands conurbation. Some of the monitoring stations are owned and operated by the Government, as part of the Automatic Urban and Rural Network (AURN). Others are owned by Local authorities, but are affiliated to the AURN. In this report, the levels of carbon monoxide, measured at AURN stations in neighbouring authorities and at Birmingham Airport, are included to demonstrate the relationship between the levels, across the conurbation. Figure 5.2 below shows the maximum 8-hour running average values recorded, in 1999, at the monitoring stations in the West Midlands. In all cases the maximum values are well below the air quality standard.

Maximum 8-Hourly Values in the West Midlands Carbon Monoxide, 1999

Figure 5.2

The trends in the maximum concentrations of carbon monoxide have been showing a progressive improvement throughout the 1990s. Although the concentrations of air pollutants vary from year to year, due to varying weather patterns, the overall levels of pollution will drop if the emissions of a pollutant are falling. Thus, as the vehicle fleet changes, due to the introduction of new vehicles with lower emissions and the removal of older vehicles with higher emissions, less carbon monoxide is emitted and the air quality improves.

Trends in West Midlands Air Qualilty Carbon Monoxide: Maximum 8-Houly Values

Figure 5.3

5.7 Future Trends in Carbon Monoxide Levels

Government now considers that the levels of carbon monoxide arising from road traffic are unlikely to present a significant risk of breaching the objective in 2003 if the daily average traffic flows are:-

• Less than 80000 vehicles per day on single carriageways,
• Less than 120000 vehicles per day on dual carriageways, or
• Less than 140000 vehicles per day on motorways.

But they also suggest that, where major roads intersect, the combined flow on both roads needs to be assessed as the flow across the junction, (LAQM TG4 (00)).

Solihull has no single or dual carriageway roads exceeding the Government criteria. Neither the M6 nor the M42 motorways exceed 140000 vehicles per day, in Solihull.

Furthermore, few of its major road intersections appear to have combined flows of more than 80000 vehicles per day. The statistics on traffic flows and the likely effects on carbon monoxide levels are illustrated by the trend in the values measured at the longest serving AURN station in the midlands, Birmingham Centre, and alongside some of the heavily trafficked roads. These values, together with predictions for future, are presented in Figure 5.4.

Forecasts for West Midlands Air Quality Carbon Monoxide: Maximum 8 Hourly Values

Figure 5.4

Since modelling studies were being undertaken for other pollutants, we were able to model the distribution and predicted concentrations of carbon monoxide. The model's predictions have been validated against measurements made within the West Midlands conurbation. Any discrepancies between the modelled and measured values have been adjusted in the maps shown below (see Stage 3 Technical Report for details).

The colour scheme used for the pollution maps is designed to demonstrate the relationship between the predicted values and the relevant carbon monoxide objective. Values near to or above the objective are displayed in orange and red. Values displayed in blue and green represent low or intermediate values so that those areas are highly unlikely to exceed the objective.

Figure 5.5 shows the predicted distribution of carbon monoxide in Solihull, based on the emissions inventory for 1998. Although the highest predictions refer to the town centre and along major radial routes, all the predicted values are well below the carbon monoxide objective.

Similarly, Figure 5.6 shows the predicted distribution of carbon monoxide in Solihull, based on the emissions inventory for 2005. This year has been chosen because it is the year with the most reliable speed-related vehicle emissions data. However, it is anticipated that the difference in emission rates between 2003 and 2005 will be marginal.

Given that the carbon monoxide levels already meet their objective now, that the trend graph suggests a gradual improvement through to 2003 and 2005, and that the pollution map for 2005 indicates compliance with the objective then, the carbon monoxide objective should also be met in 2003.

Distribution of Maximum Carbon Monoxide levels, 1998

Distribution of Maximum Carbon Monoxide levels, 2005