Per- and polyfluoroalkyl substances (PFAS) are widely used bio-accumulative chemicals in many industrial and household products. Experimental studies reported that exposure to PFAS results in immunotoxicity. We have previously reported that prenatal exposure to PFAS decreased the risk of
allergies, while it increased the risk of
infectious diseases at ages 2 and 4 years. However, it remains unclear whether the adverse effects of PFAS on
allergies and
infectious diseases continue until a reliable age of diagnosing
allergies. This study aimed at investigating the effects of prenatal exposure to PFAS on the prevalence of
allergies and
infectious diseases in children up to age 7, from the Hokkaido Study. Among mother-child pairs enrolled in the Hokkaido study and followed up until the age of 7 years, 2689 participants with maternal PFAS, 1st trimester of pregnancy and 7-year-old questionnaire survey data were included in this study. Eleven PFAS in the 3rd-trimester plasma were measured using ultra-performance liquid chromatography coupled to triple quadrupole tandem mass spectrometry. Wheeze, rhino-
conjunctivitis, and
eczema were defined using the International Study of
Asthma and
Allergies on Childhood (ISAAC) questionnaire. History childhood
infectious diseases diagnosed by a doctor was assessed by a mother-reported questionnaire at child's age 7. The relative risk of childhood
allergies was calculated by generalized estimating equation models. The odds ratio of an episode of
infectious diseases was calculated by logistic regression analysis, adjusted for potential confounders. The prevalence of various
allergies and
infectious diseases was: wheeze, 11.9%; rhino-
conjunctivitis, 11.3%;
eczema, 21.0%;
chickenpox, 61.5%;
otitis media, 55.7%;
pneumonia, 30.6%; and
respiratory syncytial virus infection, 16.8%. Prenatal exposure to
perfluorooctanoic acid,
perfluorodecanoic acid (PFDA), and
perfluoroundecanoic acid (
PFUnDA) was inversely associated with rhino-
conjunctivitis, while that for
perfluorooctanoate (PFOA),
perfluorooctane sulfonate,
PFUnDA,
perfluorododecanoic acid (PFDoDA), and
perfluorotridecanoic acid was inversely associated with
eczema. For
infectious diseases, PFDA and PFDoDA were associated with increased risk of
pneumonia and PFOA was associated with increased risk of
RSV infection among children not having any siblings (only-one-child). Our results corroborate the hypothesis on immunosuppressive and immunomodulating effects of PFAS on
allergies and
infectious diseases in children. These effects observed previously at 2 and 4 years continued until the age of 7 years. However, additional studies assessing inflammatory
biomarkers along with ISAAC questionnaires, doctor-diagnosed
allergies, and longer follow-ups are necessary to better assess the effects of exposure to chemicals on human immune outcomes.