Sunlight through residential glazing and prevention of neonatal jaundice

INTRODUCTION: Despite current guideline recommendations, the empiric recommendation to place jaundiced infants "in the sun, by the window" is commonly issued to parents to prevent or treat jaundice. MATERIAL AND METHODS: Spectral irradiance (350-1150 nm) was measured with a spectroradiometer on sunny and cloudy days. Seven residential glazing configurations commonly used in dwellings were then interposed between the sun and the sensor. For each glass type, we obtained measurements without glass and with glass (5 and 30 cm from the sensor) and calculated the relative spectral transmission. We analyzed the irradiance in the blue band (≈ 460-490 nm) and compared it with neonatal phototherapy thresholds (30-65 µW/cm²/nm). RESULTS: Direct solar irradiance reached a maximum of 2.8 W/m²/nm at 582 nm and mean values around 2.3 W/m²/nm in the 460-490 nm band on clear days, which were several times higher than intensive phototherapy thresholds. Even on cloudy days, blue irradiance remained clearly above these thresholds. Visible light transmission through glazing elements was high. Transmission did not exhibit relevant attenuation below 400 nm and increased again in the near-infrared region (>750 nm). CONCLUSIONS: Typical residential glazing elements transmit very high levels of solar irradiance, with a broad spectrum that includes UVA and infrared radiation, and blue irradiance several times higher than used in phototherapy, but without spectral selectivity or dose control. Exposing healthy newborns to sunlight through home windows cannot be considered an appropriate or safe intervention to prevent jaundice in developed countries.