Issue link: https://hi.iaq.net/i/670243
Every breath we take: the lifelong impact of air pollution developing fetus is crucially dependent on the timing in pregnancy of the infection and on which organs are developing most rapidly at that time. Infection in very early pregnancy affects the heart, but only a few days later produces permanent damage in the brain, eyes and ears. In contrast, infection near the end of pregnancy has few damaging effects. When children and adults contract German measles, it is considered to be a trivial disease, demonstrating that the sensitivity to and consequences of rubella infection are highly dependent on the stage of development. 3.2 Why are infants and young children vulnerable to the effects of air pollution? Pregnancy and early childhood are critical times for the formation and maturation of all the important body systems; there is no other time in life during which such rapid changes take place. This means that factors that exert an adverse influence on human development, including air pollution, can have a far greater influence during this period than at other times; the rapidity of change magnifies their effects, and important organ systems, once their physical development is harmed, may not have the capacity to recover. This means that organ damage that occurs as a result of harm in early life, including before birth, will be present for the rest of that individual's life. This does not always mean that such changes 38 © Royal College of Physicians 2016 1 Age of embryo (in weeks) Loss of conceptus Timing of air pollution risks: Interrupted placental development Fetal growth restriction Note: Grey bars indicate time periods when major morphological abnormalities can occur, while light-blue bars correspond to periods at risk from minor abnormalities and functional defects. Reduced weight gain Preterm birth Early susceptibility to later preterm birth Heart defects Major morphological abnormalities Functional defects and minor morphological abnormalities Dividing zygote, implantation and gastrulation CNS Heart Heart Limbs Teeth Eye Eye Ear Ear Brain Heart Heart Upper limbs Lower limbs Teeth CNS Eyes Ear Palate Palate External genitalia External genitalia Fetal period (in weeks) Full term 2 3 4 5 6 7 8 9 16 20–36 38 Fig 7. Critical periods of risk from air pollution during fetal development. CNS = central nervous system. Figure reprinted with permission. Ritz B, Willhelm M. Air pollution impacts on infants and children. UCLA Institute of the Environment: Southern California Environmental Report Card – Fall 2008, Los Angeles, CA: 2008.