# Ahlbom et al. pooled analysis of magnetic fields and childhood leukaemia (2000)

> A pooled analysis of nine studies that produced the 0.3–0.4 µT figure still cited in every ELF policy discussion, reporting roughly twice the relative risk above that level.

- Canonical URL: https://emfbase.com/studies/ahlbom-2000-pooled-childhood-leukaemia
- Collection: Research record
- Record id: `studies:ahlbom-2000`
- Status: verified
- Last verified: 2026-08-12
- JSON: https://emfbase.com/api/studies/ahlbom-2000-pooled-childhood-leukaemia

## Key values

- **Authors:** Ahlbom A, Day N, Feychting M, et al.
- **Year:** 2000
- **Design:** systematic review
- **Exposure studied:** Residential 50/60 Hz magnetic field, time-weighted average
- **Place in the evidence base:** high
- **Primary document:** https://pubmed.ncbi.nlm.nih.gov/10970686/

## Finding

No excess risk below 0.4 µT; a relative risk of about 2.0 for exposures at or above 0.4 µT, consistent across the pooled datasets.

## What it cannot establish

Very few children were in the highest exposure category, so the estimate is statistically fragile. Possible selection bias in participation, and no mechanistic explanation. Pooling reduces random error but not shared systematic error.

## Related records

- [IARC classification of ELF magnetic fields as Group 2B (2002)](https://emfbase.com/studies/iarc-2002-elf-magnetic-group-2b): IARC classified extremely low frequency magnetic fields as possibly carcinogenic to humans (Group 2B) on the basis of consistent epidemiological associations with childhood leukaemia above roughly 0.3–0.4 µT.
- [WHO/IARC ELF magnetic field association threshold (0.3–0.4 µT)](https://emfbase.com/limits/who-elf-0-3-0-4-microtesla-association): The average daily exposure level above which pooled epidemiological studies report an association with childhood leukaemia, and the basis for the IARC Group 2B classification of ELF magnetic fields.

## Sources

- `ahlbom-2000` British Journal of Cancer (2000). *A pooled analysis of magnetic fields and childhood leukaemia*. https://pubmed.ncbi.nlm.nih.gov/10970686/ — peer-reviewed, link checked 2026-08-12
- `who-elf` World Health Organization (2007). *Electromagnetic fields and public health: exposure to extremely low frequency fields*. https://www.who.int/teams/environment-climate-change-and-health/radiation-and-health/non-ionizing/exposure — government, link checked 2026-08-12

Data licence: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Dataset version 2026.08.1. Retrieved from EMFBase, https://emfbase.com.

This record is reference data, not medical or legal advice. Regulatory limits, scientific guidelines and precautionary values are labelled separately and answer different questions.