Traffic NOx linked to cervical and brain cancer risk
In 54,304 Danish adults, long-term traffic-related NOx at home was associated with cervical and brain cancer, with a weaker liver-cancer traffic signal.
Source
Air pollution from traffic and cancer incidence: a Danish cohort study
Study at a glance
- Design
- Cohort — Diet, Cancer and Health cohort with modeled residential NOx and nearby traffic load
- N
- N=54304 · 54,304 cohort members followed ~9.6 years (from 57,053 recruited)
- Population
- Danish adults aged 50–64 in Copenhagen and Aarhus areas
- Outcome
- Incidence of 20 non-lung cancers related to residential traffic pollution
Structured fields used in claim comparison tables when every cited study has a complete layer.
What they did
Using the Diet, Cancer and Health cohort, authors modeled time-weighted residential NOx from 1971 onward and traffic load within 200 m, then estimated linear IRRs for 20 non-lung cancers with cancer-specific confounder adjustment.
What they found
After adjustment, cervical and brain cancers were significantly associated with residential NOx and/or nearby major streets; brain cancer was almost doubled near high-traffic streets. Liver cancer associated with nearby traffic but not NOx. Many smoking-related IRRs shrank after confounder control. Median NOx was 21.9 μg/m³.
The limits
What it doesn't show
This was a 20-cancer screen, so false positives are possible. Cervical results lack HPV data. Tables with exact IRRs are not in the extracted text, and lung cancer was excluded because it was published separately.
Key terms
- NOx
- Nitrogen oxides used here as a modeled marker of traffic-related air pollution at the residence.
- IRR
- Incidence rate ratio from a Cox model, here per 100 μg/m³ NOx or per 10^4 vehicle-km/day nearby.
- Traffic load
- Vehicle-kilometers per day within 200 m of the home at enrolment.
- Ultrafine particles
- Particles <100 nm that can translocate from airways toward brain and other organs in animal studies.
- Hypothesis-generating screen
- Testing many cancer sites without a single pre-specified primary endpoint.
Flashcards
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The exposure marker was primarily:
Common questions
Was lung cancer included?
No. This paper screened 20 other relatively frequent cancers; lung cancer was reported separately.
Why might cervical cancer be confounded?
HPV infection and screening uptake were unmeasured, though education and smoking were adjusted.
How was exposure assigned?
A validated dispersion model of NOx at every address since 1971, plus simple traffic indicators at enrolment.
Did smoking explain the signals?
Adjustment reduced IRRs for several smoking-related cancers, but cervical and brain associations remained.
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