What is the Gera Air Health Index for Hertsmere?

Hertsmere scores 4.7/10 on the Gera Air Health Index as of 2024 (rank 255 of 296 English local authorities). That is 1.2 points below the national average of 5.9/10. This score is based on PM2.5 exposure only; no separately published mortality-fraction data is available for this lower-tier local authority.

What is the annual mean PM2.5 concentration in Hertsmere?

The population-weighted annual mean PM2.5 concentration in Hertsmere is 7.80 µg/m3 (DEFRA Pollution Climate Mapping model, 2024). This is above the WHO 2021 annual guideline of 5 µg/m3 and below the UK 2028 interim target of 10 µg/m3.

How is the Gera Air Health Index calculated for Hertsmere?

For lower-tier local authorities where UKHSA does not publish a separate mortality fraction, GAH equals the PM2.5_score alone (min-max normalised, 4.20 µg/m3 = 10, 10.96 µg/m3 = 0). Full methodology at /methodology/gera-air-health-index.

Where does the air quality data for Hertsmere come from?

PM2.5 data: DEFRA Pollution Climate Mapping (PCM) model, population-weighted annual mean for 2024, published at uk-air.defra.gov.uk. Both datasets are Open Government Licence v3.0 and reusable with attribution. The Gera Air Health Index is computed by GeraRent from these figures; the inputs are official government data.

Is the air quality in Hertsmere getting better or worse?

The 2024 figures reflect the most recent DEFRA PCM modelled annual mean. UK PM2.5 concentrations have fallen substantially since 2010 due to emission reductions, but remain above the WHO 2021 annual guideline of 5 µg/m3 in most English local authorities. Hertsmere (7.80 µg/m3) is working towards the WHO guideline. Gera updates GAH annually when DEFRA publishes new PCM data.

Air quality in Hertsmere

England · ONS code E07000098

What is the air quality and health risk from air pollution in Hertsmere?

Hertsmere has a Gera Air Health Index of 4.7/10 (rank 255 of 296 English local authorities), based on a population-weighted annual mean PM2.5 concentration of 7.80 µg/m3 in 2024 — below the UK 2028 interim target. DEFRA PCM / UKHSA Fingertips data, OGL v3.0.

Proprietary metric:Gera Air Health Index·As of 2024 · updated annual (last: 2026-06-20)

4.7/ 10

Gera Air Health Index — Hertsmere

Rank 255 of 296 English local authorities · 1.2 points below the national average of 5.9/10

Below UK 2028 target

ⓘ PM2.5 component only — no separately published health-burden data for this lower-tier local authority.

Air quality data — Hertsmere

Gera Air Health Index data for Hertsmere
Metric	Value	Source
Gera Air Health Index (GAH/10)	4.7/10	GeraRent (computed)
Annual mean PM2.5 (µg/m3)	7.80	DEFRA PCM 2024
PM2.5 sub-score (0–10)	4.7	GeraRent (normalised)
WHO 2021 guideline met?	No (7.80 > 5)	WHO Air Quality Guidelines 2021
UK 2028 interim target met?	Yes (7.80 ≤ 10)	Environment Act 2021

Population-weighted annual mean PM2.5 (2024) from DEFRA Pollution Climate Mapping (PCM) model. Every figure is real official government data — only the composite GAH score is Gera's. Full methodology.

Personal air quality risk estimator

See how Hertsmere's PM2.5 level compares to WHO and UK targets for your health profile. Adjust the sliders to explore other scenarios.

Adjust the inputs below to see how different PM2.5 levels and health profiles affect your personal air quality risk assessment. Based on DEFRA PCM data and WHO risk thresholds.

PM2.5 annual mean (µg/m3)Hertsmere: 7.80

4 µg/m3 (cleanest)7.8 µg/m315 µg/m3 (most polluted)

Health profile

Years of exposure

1 year5 years30 years

Moderate risk· PM2.5 7.8 µg/m3

Below UK 2028 interim target but above WHO guideline. Long-term exposure raises cardiovascular and respiratory risk.

Air quality comparison against thresholds
Benchmark	Level (µg/m3)	Your area vs
WHO 2021 annual guideline	5.0	56% above
UK 2028 interim target	10.0	22% below ✓
England average (approx)	8.1	4% cleaner

Estimated excess cumulative PM2.5 exposure above WHO guideline

14.0 µg/m3·years

Over 5 years at 7.8 µg/m3, adjusted for your health profile (×1.0 sensitivity factor). This is an illustrative estimate, not a clinical assessment.

PM2.5 values from DEFRA Pollution Climate Mapping (PCM) 2024, population-weighted. Risk thresholds: WHO Air Quality Guidelines 2021. Health-profile sensitivity factors are illustrative multipliers based on published vulnerability evidence (WHO, COMEAP), not personalised clinical advice. Consult a healthcare professional for personal health guidance.

Hertsmere air quality — questions and answers

What is the Gera Air Health Index for Hertsmere?: Hertsmere scores 4.7/10 on the Gera Air Health Index as of 2024 (rank 255 of 296 English local authorities). That is 1.2 points below the national average of 5.9/10. This score is based on PM2.5 exposure only; no separately published mortality-fraction data is available for this lower-tier local authority.
What is the annual mean PM2.5 concentration in Hertsmere?: The population-weighted annual mean PM2.5 concentration in Hertsmere is 7.80 µg/m3 (DEFRA Pollution Climate Mapping model, 2024). This is above the WHO 2021 annual guideline of 5 µg/m3 and below the UK 2028 interim target of 10 µg/m3.
How is the Gera Air Health Index calculated for Hertsmere?: For lower-tier local authorities where UKHSA does not publish a separate mortality fraction, GAH equals the PM2.5_score alone (min-max normalised, 4.20 µg/m3 = 10, 10.96 µg/m3 = 0). Full methodology at /methodology/gera-air-health-index.
Where does the air quality data for Hertsmere come from?: PM2.5 data: DEFRA Pollution Climate Mapping (PCM) model, population-weighted annual mean for 2024, published at uk-air.defra.gov.uk. Both datasets are Open Government Licence v3.0 and reusable with attribution. The Gera Air Health Index is computed by GeraRent from these figures; the inputs are official government data.
Is the air quality in Hertsmere getting better or worse?: The 2024 figures reflect the most recent DEFRA PCM modelled annual mean. UK PM2.5 concentrations have fallen substantially since 2010 due to emission reductions, but remain above the WHO 2021 annual guideline of 5 µg/m3 in most English local authorities. Hertsmere (7.80 µg/m3) is working towards the WHO guideline. Gera updates GAH annually when DEFRA publishes new PCM data.

Other England local authorities

See the full national Gera Air Health Index ranking, or explore overall liveability scores including schools, safety, broadband and house prices.

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PM2.5 source: DEFRA Pollution Climate Mapping (PCM) model, population-weighted annual mean 2024 (popwmpm252024byUKlocalauthority.csv), uk-air.defra.gov.uk/data/pcm-data. Open Government Licence v3.0. The Gera Air Health Index is computed by GeraRent; full methodology at /methodology/gera-air-health-index.