Air pollution exposure during pregnancy increases risk of neurodevelopmental disorders

Emerging evidence in large population- based epidemiological studies indicates that exposure to a specific type of air pollution – fine particulate matter less than 2.5 microns in diameter (PM 2.5 ) – during gestation increases the risk of neurodevelopmental disorders. 1 Shih et al. report an association between neurodevelopmental delays and increased gestational exposure to ambient PM 2.5 in a large population- based sample of 17 638 individuals. 2 Shih et al. found that PM 2.5 exposure increased the risks for delayed gross motor development, fine motor development, and personal– social skills. 2 Notably, Shih et al. also report the lack of association between early postnatal PM 2.5 exposure and neurodevelopmental delays. 2 These data support a recurring theme in the literature: that the impact of PM 2.5 air pollution exposure occurs during gestation rather than after birth. It might seem counterintuitive that the impact of air pollution is greater in the womb than when the child has direct access to air pollution. The developing brain in the womb would seem to be better protected from air pollution, as toxic chemicals

levels during pregnancy are strongly correlated with particulate matter in the placenta and cord blood. These data provide strong evidence that the fetus is exposed to the same air pollution as the mother during pregnancy.
The observations that neurodevelopmental disorders are caused by PM 2.5 exposure during gestation but not during the early postnatal years suggest a critical period for neurodevelopment that occurs before birth. The impacts of air pollution exposure on brain development during gestation are particularly harmful because the basic building blocks of the forebrain are rapidly generated during the second trimester of gestation. The differentiating brain cells must assume one of multiple neural identities, migrate to their proper positions, and make synaptic connections. If neurodevelopment is disrupted early during that process -during a critical period -then the opportunities for compensation are limited. Imaging studies indicate that PM 2.5 exposure during early childhood changed thickness and surface area in several regions of cerebral cortex, but did not find an impact on measures of neurocognition. These data provide further evidence that, even though postnatal PM 2.5 exposure after birth alters brain structure, the critical period for neurocognition occurs during gestation.
There is now ample epidemiological evidence that PM 2.5 exposure during gestation contributes to neurodevelopmental disorders. However, the mechanisms by which PM 2.5 changes neurodevelopment are poorly understood. Gestational exposure of mice to air pollution particulate matter caused decreased neurogenesis in the hippocampal dentate gyrus, increased depressive behaviors, and a malespecific increased glucose tolerance in the offspring. 4 These data implicate altered neurogenesis in a behavioral outcome. Similarly, human cerebral organoids exposed to air pollution particulate matter demonstrate altered mitochondrial function in outer radial glia cells, indicating perturbation of fundamental cellular proliferation and metabolism in a cell type critical for neuronal migration and differentiation. 5 Future studies will be required to determine the mechanisms by which PM 2.5 exposure (specifically during gestation) contributes to neurodevelopmental disorders through lasting impacts on neuronal lineages and their dependent neural circuits.

Findings from the British Childhood Visual Impairment and Blindness Study 2: Implications for children in low-income countries Guy Le Fanu
Sightsavers, Haywards Heath, UK Fully sighted children use their vision to carry out various activities and engage with the world around them. As a result, they acquire various capacities, establish new and closer relationships, and develop a sense of self-efficacy. Children with visual impairments may find it difficult or impossible to carry out these activities or may be discouraged from doing so because of their lack of sight. Multidisciplinary teams can assist these children to overcome these challenges and realize their potential, either through directly supporting the child or providing their caregivers with the necessary guidance and reassurance. It is therefore concerning that the British Childhood Visual Impairment and Blindness Study 2 found a significant proportion of children newly diagnosed as blind or severely visually impaired in the UK had not received an Education, Health, and Care Plan or support from multidisciplinary teams/appropriately trained education specialists. 1 Children with moderate visual impairments had even less access to such provision. In the light of these findings, Solebo et al. make a persuasive case for increased investment in health, education, and social care provision. Their case would be even more compelling if qualitative research was carried out, both among the families accessing and the families denied this provision, to assess the impact (or the lack of it) on their well-being. Such research might also reveal additional needs among these families -for instance, greater access to social housing of good quality or increased disability living allowances.
Solebo et al. refer to the challenges faced by service providers in middle-income countries where there are growing numbers of children with visual impairments with additional support needs (a consequence of improved survival rates). 1 It is also worth considering the case of low-income countries such as Malawi. Although no comprehensive situation analysis has been carried out of services for children with visual impairments in this country, the available evidence suggests that they are few and far between and often of poor quality. For instance, researching in southern Malawi, Lynch et al. found a significant proportion of children aged 0 to 6 years reported as visually impaired had not been formally diagnosed. 2 While there are health surveillance assistants in every district responsible for carrying out various health tasks (including early childhood development), Gladstone et al. found that the six health surveillance assistants studied were responsible for 420 children (disabled and non-disabled) under 2 years. 3 Although there are between 5000 to 6000 community-based childhood care centres providing preschool education for children aged 3 to 5 years (mainly in rural areas), these centres lack financial, material, and human resources. 4 A pilot project in Malawi has trained community workers to assist primary caregivers to bond with and stimulate children with visual impairments. 2 In addition, Sightsavers,