Pollution Control
Air Quality
Withyhedge Air Quality Monitoring
Weekly reports:
1 October
Withyhedge landfill site hydrogen sulphide monitoring survey - 1st October
8 October
Withyhedge landfill site hydrogen sulphide monitoring survey-8th October
Historical reports
Historical Air Quality reports
On this page:
Air quality progess report 2023
Report 5: Executive summary
This interim report summarises the data gathered from the ongoing monitoring around Withyhedge Landfill. The monitoring includes diffusion tubes for the assessment of Hydrogen Sulphide and Volatile Organic Compounds (VOCs) that provide averaged concentrations over a defined period, and instantaneous measurements of Hydrogen Sulphide using a Jerome analyser. The monitoring programme is primarily aimed at gathering quantitative data to provide lines of evidence to help assess risks from the exposure to off-site air quality.
Comparison of the Hydrogen Sulphide concentrations detected using diffusion tubes with health-based criteria indicates that the concentrations continue to be below the guidance values for intermediate/lifetime exposure. At many positions Hydrogen Sulphide is not found above the analytical level of detection.
Monitoring of Volatile Organic Compounds (VOC) has also revealed many VOCs to be present at very low levels and below evaluation criteria, where available.
Using a hand-held instrument, known as a Jerome, Hydrogen Sulphide concentrations have been logged at different locations. Many readings are below the detection limit and a 30- minute nuisance threshold of 5 ppb has not been exceeded throughout the latest monitoring period. In combination, the data suggests that Hydrogen Sulphide is either not present at detectable levels or present at very low levels that fall below available guideline values.
Air quality monitoring interim summary report - 5
Report 4: Executive summary
This interim report summarises the data gathered from the ongoing monitoring around Withyhdege Landfill. The monitoring now includes diffusion tubes for the assessment of Hydrogen Sulphide and Volatile Organic Compounds (VOCs) that provide averaged concentrations over a defined period and instantaneous measurements of Hydrogen Sulphide using a Jerome analyser. The monitoring programme is primarily aimed at gathering quantitative data to provide lines of evidence to help assess risks from the exposure to off-site air quality.
Comparison of the Hydrogen Sulphide concentrations detected using diffusion tubes with health-based criteria indicates that the concentrations continue to be below the guidance values for intermediate/lifetime exposure.
Monitoring of Volatile Organic Compounds (VOC) has revealed many VOCs to be present at very low levels and below evaluation criteria, where available. This monitoring is to cease.
Using a hand-held instrument, known as a Jerome, Hydrogen Sulphide concentrations have been logged at different locations. Many readings of Hydrogen Sulphide reported by the Jerome analyser during the latest monitoring period are close to or below the detection limit and there are few recorded values above a 5ppb guideline value. It is evident from the repeated use of the instrument at different times of the day over several days that such concentrations are not persistent over such time-frames. At many monitoring positions on different occasions the Jerome did not detect Hydrogen Sulphide above the level of detection.
Air quality monitoring summary report - 4
Report 3: Executive summary
This interim report summarises the data gathered from the ongoing monitoring around Withyhdege Landfill. The monitoring now includes diffusion tubes for the assessment of Hydrogen Sulphide and Volatile Organic Compounds (VOCs) that provide averaged concentrations over a defined period and instantaneous measurements of Hydrogen Sulphide using a Jerome analyser. The monitoring programme is primarily aimed at gathering quantitative data to provide lines of evidence to help assess risks from the exposure to off-site air quality that is impacted by the landfill.
Comparison of the Hydrogen Sulphide concentrations detected using diffusion tubes with health-based criteria indicates that the concentrations continue to fall below these guidance values for intermediate/lifetime exposure.
For the first time, monitoring of Volatile Organic Compounds (VOC) has been undertaken during the latest exposure period. The testing has revealed many VOCs to be present at very low levels and below evaluation criteria, where available.
Using a hand-held instrument, known as a Jerome, Hydrogen Sulphide concentrations have been logged at different locations. In combination with an assessment of the odour perceived at the time of sampling, this monitoring has revealed variations in the concentration of Hydrogen Sulphide, but the dataset is complex and many readings are close to the detection limit of the instrument. Higher values of Hydrogen Sulphide reported by the instrument are typically associated with the presence of odour and several different types of odour have been observed. At times, the Hydrogen Sulphide concentration has been found to be higher than 5ppb with almost 15ppb detected in the community areas for short durations (<30 minutes) and higher concentrations at the landfill site. Concentrations above 5ppb have been found associated with different odour sources including landfill gas and agricultural activities. The highest concentrations of Hydrogen Sulphide tend to be found when odorous landfill gas is suspected to be present.
Air quality monitoring summary report - 3
Report 2: Executive summary
This is the second interim reporting summarising the data gathered from the ongoing monitoring around Withyhdege Landfill. The monitoring now includes diffusion tubes for the assessment of Hydrogen Sulphide and Volatile Organic Compounds (VOCs) that provide averaged concentrations over a defined period and instantaneous measurements of Hydrogen Sulphide using a Jerome analyser. The monitoring programme is primarily aimed at gathering quantitative data to provide lines of evidence to help assess risks from the exposure to off-site air quality that is impacted by the landfill.
Comparison of the Hydrogen Sulphide concentrations detected using diffusion tubes with health-based criteria indicates that the concentrations continue to fall below these guidance values for intermediate/lifetime exposure.
For the first time, monitoring of Volatile Organic Compounds (VOC) has been undertaken during the latest exposure period. The testing has revealed many VOCs to be present at very low levels and below evaluation criteria, where available.
Using a hand-held instrument, known as a Jerome, Hydrogen Sulphide concentrations have been logged at different locations. Initial consideration of the data gathered indicates that the values recorded have been above and below a 5ppb guideline value and that these values have been recorded when an odour is detectable / reported and at times when an odour has not been detectable. Ongoing monitoring using the Jerome is focussing on logging data for 30-minutes at 5-minute sampling intervals at the same position as the diffusion tubes. This data will be evaluated in the next data monitoring summary alongside a comparison of the results gathered by different Jerome monitors.
Air quality monitoring summary report - 2
Report 1: summary
Air quality monitoring summary report - 1
Public Health Wales Evaluation (opens in a new tab)
The attached tables show a summary of the monitoring results showing 30 minute averages
Table A
Date |
Start time of monitoring |
Location |
30 minute average concentration (ppb) compare to WHO ST level of 5 ppb |
Wind direction (from) |
Wind direction likely to impact at receptor |
Wind speed |
| 08-May | 00:09:26 | B4329 Junction - Poyston Cross what3words = wound.hardening.butternut |
0.4 | No wind | N/NNW | No wind |
| 08-May | 07:20:48 | Corner Piece Inn | 13.5 | No wind | W/WSW | No wind |
| 12-May | 22:26:26 | SA62 5QR - Opposite Oakvale, Spittal what3words = truly.creatures.smoker |
2.0 | South South West / South | S/SW | Light |
| 14-May | 14:03:26 | Corner Piece field what3words - stud. Supplied. Strongman Location chosen due to landfill odours. |
2.2 | South East | W/WSW | Light |
| 26-May | 08:03:01 | 6) Spittal Primary School | 0.0 | South West | S/SW | None - Light |
| 10-Jun | 04:25:06 | what3words: expansion.traffic. fondest | 4.8 | North West | N/NNW | Steady/Strong |
Table B
21st March 24
Start time of monitoring |
Location |
30 minute average concentration (ppb) compare to WHO ST level of 5 ppb |
Odour detected |
Wind direction (from) |
Wind speed |
Wind direction likely to impact at receptor |
Site activities or other activities |
Notes / commentary |
| 10:04:13 | D4 | 3.0 | Intermittent 'sweet' odour | no data | no data | SW | no data | not applicable |
| 10:44:21 | Spittal School | 20.2 | Intermittent odour | no data | no data | S/SW | no data | Includes a very high reading for first 5 minutes (117.07 ppb) of the monitoring period. If following the user manual the first 5 minute warmup cycle would not be included. |
| 11:29:09 | Treffgarne (adjacent church) | 0.8 | No detectable odour | no data | no data | S/SE | no data | not applicable |
| 13:51:15 | D9 | 0.0 | No detectable odour | no data | no data | E | no data | not applicable |
| 14:37:59 | D1 | 3.7 | No detectable odour | no data | no data | S | no data | not applicable |
| 15:25:14 | Opposite Spittal School | 3.9 | Intermittent odour | no data | no data | S/SW | no data | not applicable |
| 16:17:43 | Withybush Road, South of Haverfordwest | 4.3 | Intermittent odour | no data | no data | N | no data | not applicable |
22nd March 2024
Start time of monitoring |
Location |
30 minute average concentration (ppb) compare to WHO ST level of 5 ppb |
Odour detected |
Wind direction (from) |
Wind speed |
Wind direction likely to impact at receptor |
Site activities or other activities |
Notes / commentary |
| 10:22:18 | Treffgarne (adjacent church) | 22.0 | No odour detectable | NW | no data | S/SE | no data | not applicable |
| 11:13:16 | Spittal school | 4.1 | Weak odour | W | no data | S/SW | no data | not applicable |
| 12:00:03 | D6 | 4.1 | No odour | NW | no data | W | no data | not applicable |
| 13:03:03 | D7 | 3.9 | No odour | W | no data | N/NNE | no data | not applicable |
3rd April 2024
Start time of monitoring |
Location |
30 minute average concentration (ppb) compare to WHO ST level of 5 ppb |
Odour detected |
Wind direction (from) |
Wind speed |
Wind direction likely to impact at receptor |
Site activities or other activities |
Notes / commentary |
| 12:01:23 | Ell's Kitchen | 2.9 | Weak odour | N | no data | N | no data | not applicable |
| 12:55:53 | A40 Rudbaxton Junction | 4.5 | Strong impersistent odour | N | no data | N | no data | not applicable |
| 14:05:53 | Spittal school | 4.1 | Impersistent 'sweet' odour | W | no data | S/SW | no data | not applicable |
| 15:15:53 | D7 | 4.0 | No odour detectable | N | no data | N | no data | not applicable |
5th April 2024
Start time of monitoring |
Location |
30 minute average concentration (ppb) compare to WHO ST level of 5 ppb |
Odour detected |
Wind direction (from) |
Wind speed |
Wind direction likely to impact at receptor |
Site activities or other activities |
Notes / commentary |
| 10:25:53 | HfW County Hall | 5.1 | No odour | Gusting wind | no data | N/NNE | no data | Not enough data to calculate a 30 minute average - 25 minutes worth |
| 11:45:52 | Treffgarne (adjacent church) | 5.0 | Faint intermittent odour | E | no data | SE | Agri? | Not enough data to calculate a 30 minute average - 25 minutes worth |
| 12:30:52 | D1 | 4.9 | Sweet' odour | S/SW | no data | S | Agri? | not applicable |
| 13:15:53 | Spittal school | 6.7 | Strong odour, pungent, landfill | S/SW | no data | S/SW | no data | not applicable |
| 15:40:52 | D7 | 4.6 | No odour | S | no data | N/NNE | no data | not applicable |
| 16:40:52 | Palmerston Rd, Haverfordwest | 5.1 | No odour | S | no data | no data | no data | Not enough data to calculate a 30 minute average - 25 minutes worth |
16th April 2024
Start time of monitoring |
Location |
30 minute average concentration (ppb) compare to WHO ST level of 5 ppb |
Odour detected |
Wind direction (from) |
Wind speed |
Wind direction likely to impact at receptor |
Site activities or other activities |
Notes / commentary |
| 10:15:52 | Spittal school | 5.5 | Weak odour | W/NW | no data | S/SW | no data | not applicable |
| 11:40:52 | Poyston cross | 8.3 | Strong pungent odour | W/NW | no data | N/NE | no data | not applicable |
23rd April 2024
Start time of monitoring |
Location |
30 minute average concentration (ppb) compare to WHO ST level of 5 ppb |
Odour detected |
Wind direction (from) |
Wind speed |
Wind direction likely to impact at receptor |
Site activities or other activities |
Notes / commentary |
| 14:05:52 | Spittal school | 0.5 | No odour | NW | no data | S/SW | no data | not applicable |
| 14:55:53 | D7 | 2.8 | Faint intermittent unknown odour | NW | no data | N/NE | no data | not applicable |
24th April 2024
Start time of monitoring |
Location |
30 minute average concentration (ppb) compare to WHO ST level of 5 ppb |
Odour detected |
Wind direction (from) |
Wind speed |
Wind direction likely to impact at receptor |
Site activities or other activities |
Notes / commentary |
| 09:00:52 | D10 | 3.9 | Weak intermittent odour | no data | no data | E/ESE | no data | not applicable |
| 09:40:52 | D1 | 4.8 | Sweet' odour | no data | no data | S | Agri? | not applicable |
| 10:30:52 | D2 | 3.1 | Faint odour | no data | no data | S/SW | Agri? | not applicable |
| 11:10:53 | D3 | 4.3 | No odour | no data | no data | S/SW | no data | not applicable |
| 11:50:52 | D4 | 4.5 | Faint odour | no data | no data | SW | no data | not applicable |
| 12:40:52 | D5 | 4.8 | Faint odour | no data | no data | W | Agri? | not applicable |
| 13:20:52 | D6 | 4.9 | No odour | no data | no data | W | no data | Not enough data to calculate a 30 minute average - 25 minutes worth |
| 13:55:52 | D7 | 4.2 | Faint odour | no data | no data | N/NNE | no data | not applicable |
| 14:35:52 | D8 | 4.7 | No odour | no data | no data | NE | no data | not applicable |
| 15:20:52 | D9 | 4.8 | Faint odour | no data | no data | NNE | no data | not applicable |
26th April 2024
Start time of monitoring |
Location |
30 minute average concentration (ppb) compare to WHO ST level of 5 ppb |
Odour detected |
Wind direction (from) |
Wind speed |
Wind direction likely to impact at receptor |
Site activities or other activities |
Notes / commentary |
| 13:15:53 | D9 | 6.4 | Faint odour | no data | no data | NE | no data | not applicable |
| 13:55:52 | D10 | 3.8 | Strong odour | no data | no data | NNE | no data | not applicable |
| 14:40:53 | D1 | 0.0 | Intermittent odour | no data | no data | NNE | no data | not applicable |
29th April 2024
Start time of monitoring |
Location |
30 minute average concentration (ppb) compare to WHO ST level of 5 ppb |
Odour detected |
Wind direction (from) |
Wind speed |
Wind direction likely to impact at receptor |
Site activities or other activities |
Notes / commentary |
| 11:05:53 | D10 | 5.8 | None | 180 (S) | 1.1 | E/ESE | no data | not applicable |
| 11:05:53 | D1 | 6.7 | Distinct | 180 (S) | 2.9 | S | Landfill | not applicable |
| 12:30:52 | D2 | 5.2 | None | 180 (S) | 5.8 | S/SW | no data | not applicable |
| 13:10:52 | D3 | 5.5 | Distinct | 180 (S) | 3.8 | S/SW | Slurry | not applicable |
| 13:50:52 | D4 | 4.9 | Faint | 180 (S) | 3.6 | SW | Manure | not applicable |
| 14:50:53 | D8 | 4.8 | None | 180 (S) | 3.1 | NE | no data | not applicable |
| 15:40:52 | D9 | 4.3 | None | 180 (S) | 0.4 | NNE | no data | not applicable |
| 16:25:53 | D7 | 4.7 | None | 180 (S) | 1.3 | N/NNE | no data | not applicable |
| 17:15:52 | D6 | 4.2 | None | 210 (SW) | 0.4 | W | no data | not applicable |
30th April 2024
Start time of monitoring |
Location |
30 minute average concentration (ppb) compare to WHO ST level of 5 ppb |
Odour detected |
Wind direction (from) |
Wind speed |
Wind direction likely to impact at receptor |
Site activities or other activities |
Notes / commentary |
| 12:15:52 | D9 | 6.0 | Faint | 160 (SE) | 0.1 | NNE | Landfill | not applicable |
| 13:10:52 | D5 | 6.1 | Faint | 140 (SE) | 0.6 | W | Dung/nearby field | not applicable |
| 13:55:52 | D3 | 6.7 | Faint | 160 (SE) | 1.1 | S/SW | Slurry/dairy farm | not applicable |
| 14:50:52 | Treffgarne | 6.9 | Distinct | 160 (SE) | 0.1 | SE | Landfill | not applicable |
Air quality
The Environment Act 1995 and subsequent Regulations require Local Authorities to review and assess air quality in their area by the production of Updating and Screening Assessments every three years and annual Progress Reports for the intervening years. This Review and Assessment procedure represents the system for Local Air Quality Management (LAQM) which itself represents the main methodology in the UK Government's and the Devolved Administrations strategies to achieve relevant air quality objectives for Benzene, 1,3 Butadene, Carbon Monoxide, Lead, Nitrogen Dioxide, Particles and Sulphur Dioxide.
Pembrokeshire County Council carries out monitoring a range of locations within the County. The methods employed for monitoring include passive diffusion tubes, active samplers and real-time automatic analysers. The Authority manages a continuous monitoring site at Narberth which is affiliated to the UK Automatic Urban and Rural Network (operated by the Department for Environment, Food and Rural Affairs). The Welsh Air Quality Forum website (opens in a new tab) provides direct access to real-time and historic monitoring data along with relevant air quality information.
If LAQM identifies an exceedance of an objective then the Local Authority must define an Air Quality Management Area (AQMA) and attempt to develop a strategy to reduce the pollutant of concern. Presently motor vehicle emissions are presenting the greatest challenge for Local Authorities throughout the UK.
The Council remains committed to obtaining information on air quality in the area, and to carrying out its local air quality management duties, including the ongoing review and assessment of air quality in the County.
Air Quality Progress Report 2023
In pursuing its duty and commitment to monitor and improve local air quality in relation to public health and the environment the Local Authority have recognised two Air Quality Management Areas (AQMA) in Pembrokeshire; within the commercial main street areas of Haverfordwest and Pembroke. Road traffic is the principle contributor of emissions resulting in the declaration of the AQMA's due to the high concentrations of nitrogen dioxide. Both the locations are subject to the "canyon effect" where there are high sided buildings on either side of a narrow road which results in a low available dispersion of the local air. This has resulted in an exceedance of the European Union annual mean Air Quality Objective for nitrogen dioxide of 40µg/m³ taking place. Declaration and assessment of an AQMA identifies the extent of the affected area and enables the Local Authority to develop an Air Quality Action Plan to explore short and long-term measures to improve the air quality and comply with the relevant air quality objective.
Pollution Control
Tel: 01437 764551
Email: ContactCentre@pembrokeshire.gov.uk