Table 3

Exposure estimates available in the HELIX entire cohort and subcohort

Exposure groupDescription*Pregnancy
(and specific trimesters)*
0–5 years
6–11 years
Outdoor and urban exposure estimates available in the entire cohort and in the subcohort
 Atmospheric pollutantsNO2, PM2.5, PM10, PM2.5 (absorbance ratio)√ *
 Ultraviolet (UV)Ambient UV radiation levels
 Surrounding natural spaceAverage normalised difference vegetation index within buffers of 100, 300 and 500 m
Size of and distance to nearest major green or blue space (>5000 m2)
Presence of a major green or blue space in a distance of 300 m
 MeteorologyLand surface temperature average in a buffer of 50 m
Temperature from meteorological stations (mean, minimum and maximum)
Humidity percentage from meteorological stations
Atmospheric pressure data from the ESCAPE project
√ *
 Built environmentPopulation density: inhabitants per km2
Building density: built area in m2 per km2 within 100 and 300 m buffers
Street connectivity: number of road intersections per km2 within 100 and 300 m buffers
Accessibility: metres of bus public transport lines and number of bus public transport stops per km2 within 100, 300 and 500 m buffers
Facilities: facility richness index and facility density index in a 300 m buffer
Land use evenness index
Walkability index in 300 m buffer*
 TrafficTotal traffic load of major roads in a 100 m buffer, total traffic load in a 100 m buffer, traffic density on nearest road and inverse distance to nearest road
 Road traffic noiseDay and night time road noise levels
Contaminant exposure estimates available in the HELIX subcohort
 Organochlorine compoundsBlood concentrations of dichlorodiphenyldichloroethylene, dichlorodiphenyltrichloroethane, hexachlorobenzene and polychlorinated biphenyl—118, 68, 153, 170, 180. With and without lipid adjustment.
 Brominated compoundsBlood concentrations of polybrominated diphenyl ether—47, 153. With and without lipid adjustment.
 Perfluorinated alkylated substancesBlood concentrations of perfluorooctanoate, perfluorononanoate, perfluoroundecanoate, perfluorohexane sulfonate, perfluorooctane sulfonate
 Metals and essential elementsWhole blood concentrations of arsenic, cadmium, cesium, cobalt, copper, lead, manganese, mercury, molybdenum, thallium, potassium, magnesium, sodium, selenium and zinc
 Phthalate metabolitesUrine concentrations of monoethyl phthalate, mono-iso-butyl phthalate, mono-n-butyl phthalate, mono benzyl phthalate, mono-2-ethylhexyl phthalate, mono-2-ethyl-5-hydroxyhexyl phthalate, mono-2-ethyl-5-oxohexyl phthalate, mono-2-ethyl 5-carboxypentyl phthalate, mono-4-methyl-7-hydroxyoctyl phthalate, mono-4-methyl-7-oxooctyl phthalate. With and without creatinine adjustment.
 PhenolsUrine concentrations of methyl paraben, ethyl paraben , bisphenol A, propyl paraben, N-butyl paraben, oxybenzone, triclosan. With and without creatinine adjustment.
 Organophosphate pesticide metabolitesUrine concentrations of dimethyl phosphate, dimethyl thiophosphate, dimethyl dithiophosphate, diethyl phosphate, diethyl thiophosphate, diethyl dithiophosphate. With and without creatinine adjustment.
 Tobacco smokingUrine levels of cotinine. Questionnaire on active and passive smoking.
 Water disinfection by-productsTotal concentration of total trihalomethanes (THMs), chloroform and total brominated THMs estimated in tap water from water company concentration and distribution data.
 Indoor airPrediction models for indoor air concentrations of NO2, PM2.5, PMabs, benzene and toluene, ethylbenzene, xylene using panel study data from indoor air samplers.
  • *Walkability indicator adapted from the previous walkability indexes45 46: calculated as the mean of the deciles of population density, street connectivity, facility richness index and land use Shannon’s Evenness Index within 300 m buffers, giving a walkability score ranging from 0 to 1.

  • ESCAPE, European Study of Cohorts for Air Pollution Effects; HELIX, Human Early Life Exposome; NO2, nitrogen dioxide; PM2.5, mass concentration of particles <2.5 µm in aerodynamical diameter; PM10, mass concentration of particles <10 µm in aerodynamical diameter; PMabs, absorbance of PM2.5 filters; a proxy for elemental carbon, which is the dominant light absorbing substance.