From: Grass pollen allergy in children and adolescents-symptoms, health related quality of life and the value of pollen prognosis
Threshold level (pollen grains per cubic metre)
Levels
Britain/Denmark
Sweden
Traffic lights
Low
1–30
0–10
0–30
Moderate
31–50
11–30
31–80
High
51–150
31–100
81–
Very High
150–
101–