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Is Air Pollution Associated with Increased Risk of Dementia? A Meta-Analysis of Epidemiological Research.
Dhiman, V, Trushna, T, Raj, D, Tiwari, RR
Neurology India. 2022;70(3):1004-1019
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Several studies have indicated that there may be a link between exposure to air pollution and the development of dementia. This study aimed to perform a systematic review and meta-analysis to determine the risk of developing dementia, cognitive decline, and/or Alzheimer’s disease (AD) following air pollution exposure. The results showed that exposure to small particulate matter (less than 2.5 micro m) was a risk factor for the development of dementia, AD and dementia caused by blockages in the blood vessels leading to the brain. Exposure to ozone was a risk factor for AD. Carbon monoxide, large particulate matter (10 micro m and less), nitrogen dioxide, nitrous oxides, and sulphur dioxide exposure was not a risk factor for any dementia related diseases. It was concluded that exposure to certain types of pollution may be detrimental to brain health and further research is required in developing countries, where pollution exposure can be particularly high. This study could be used by health care professionals to make informed decisions on the control of air pollution in those who are at risk of developing dementia or who are already suffering from this disease. The introduction of plants and air purifiers may be of benefit to those who are vulnerable.
Abstract
BACKGROUND There are prevailing inconsistencies in epidemiological research about air pollution being a risk factor for dementia. OBJECTIVE We performed meta-analyses to calculate the pooled estimates of the risk of developing dementia due to air pollution exposure. METHODS AND MATERIALS We performed a systematic search in PubMed, Google Scholar, The Cochrane Library, and J-GATEPLUS databases for peer-reviewed epidemiological studies reporting the risk of developing all-cause dementia, cognitive decline, Alzheimer's disease (AD), and vascular dementia (VaD) due to exposure to particulate matter with an aerodynamic diameter less than 2.5 μm (PM2.5) and less than 10 μm (PM10), ozone (O3), carbon monoxide (CO), nitrogen dioxide (NO2), nitrogen oxides (NOX) and sulfur dioxide (SO2) from the beginning until December 2020. Meta-analysis was performed by adopting the random-effects model using Meta-XL. RESULTS In all-cause dementia, the pooled hazard ratio (HR) for PM2.5 and NO2 exposure was 1.03 [(95%CI: 1.01-1.06; I2 = 99% (P < 0.001)] and 1.00 [(95%CI: 1.00-1.01; I2 = 96% (P < 0.001)], respectively. The pooled HR for NOX was 1.00 [(95%CI: 1.00-1.01; I2 = 61% (P = 0.05)]. In AD, the pooled HRs for PM2.5 and O3 was 1.08 (95%CI: 1.01-1.15; I2 = 99% (P < 0.001)]) and 1.02 (95%CI: 0.96-1.08; I2 = 100% (P < 0.001)], respectively. In VaD, the pooled HR for PM2.5 exposure was 1.03 (95%CI: 1.01-1.06; I2 = 91% (P < 0.001)]. In NO2/NOX, the results were found to be equivocal. Meta-analysis could not be performed in cognitive decline because of wide variations in assessments methods. CONCLUSIONS The present study showed exposure to PM2.5 as a risk factor for all-cause dementia, AD, and VaD and exposure to O3 as a possible risk factor for AD. These findings can be used for policy measures and further research.
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Respiratory and Allergic Effects in Children Exposed to Pesticides-A Systematic Review.
Buralli, RJ, Dultra, AF, Ribeiro, H
International journal of environmental research and public health. 2020;17(8)
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Agricultural pesticides are harmful chemicals used to protect plants from pests and diseases. There has been previous research showing a link between pesticide usage and respiratory symptoms, asthma, allergies, and lung function irregularities in children. To evaluate the relationship between pesticide usage and allergic and respiratory effects in children, 21 studies were included in this systematic review. This systematic review reports an association between multiple sources of pesticide exposure during fetal and early development and respiratory symptoms and allergies among children. Compared to high-income countries, children in the middle- and low-income countries were exposed to multiple pesticide sources. As current scientific evidence is sparse, more research is needed to determine the causal relationship between pesticides and respiratory and allergic symptoms in children. Robust research in low- and middle-income countries is necessary. Healthcare professionals can use the results of this study to understand the harmful effects of pesticide exposure in children and to take clinical decisions to reduce the exposure and its effects.
Abstract
Pesticide exposure may affect children's respiratory and allergic health, although results from epidemiological studies have not reached consensus. This review aims to analyze the scientific evidence on respiratory and allergic effects of exposure to agricultural pesticides in children aged up to 12 years old. The databases PubMed, Web of Science, Scielo, and Lilacs were screened to select articles published in English, Spanish, or Portuguese, and 21 articles were included in this review. Most investigations were conducted in North America (mostly in the United States), while no studies conducted in Latin America or Africa were found, despite their intensive use of pesticides. Children are exposed to pesticides through multiple pathways from the prenatal period throughout later developmental stages and may experience several respiratory effects. Most studies (79%) found positive associations with pesticide exposure and children's respiratory and allergic effects such as asthma, wheezing, coughs, acute respiratory infections, hay fever, rhinitis, eczema, chronic phlegm, and lung function impairments. Contrastingly, 21% of the studies found no associations between pesticide exposure and children's respiratory health. The vast differences among the characteristics of the studies hamper any comparison of the results. Exposure to pesticides may have several impacts on childhood respiratory health. More studies must be conducted, especially in low- and middle-income countries, preferably with comparable research protocols adapted to local realities. Efforts should be made to develop comprehensive risk mitigation strategies and behavioral interventions to reduce children's exposure to pesticides used in agriculture and respiratory health effects, and to ensure healthy childhood growth.
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Fluoride exposure and kidney and liver function among adolescents in the United States: NHANES, 2013-2016.
Malin, AJ, Lesseur, C, Busgang, SA, Curtin, P, Wright, RO, Sanders, AP
Environment international. 2019;132:105012
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Fluoride is added to the water supply in some parts of the UK, US and Canada to help prevent tooth decay, but there is some concern that long-term exposure to fluoride could be harmful to health. Animal studies have indicated that fluoride may cause kidney and liver damage. This US study aimed to evaluate whether greater fluoride exposure is associated with altered kidney and liver function in adolescents. This cross-sectional study looked at data collected from the National Health and Nutrition Examination Survey (2013-2016). The average age of adolescents was 15 years. Fluoride levels were measured in blood and in household tap water. Higher levels of fluoride in the blood were associated with a lower estimated glomerular filtration rate, a higher blood uric acid concentration, and a lower blood urea nitrogen concentration. Higher levels of fluoride in tap water were associated with a lower blood urea nitrogen concentration. The researchers concluded that fluoride exposure may contribute to complex changes in kidney and liver function in US adolescents. However, researchers could not rule out the possibility that an altered kidney or liver function may impact the body’s ability to absorb or metabolise fluoride.
Abstract
BACKGROUND Hepato- and nephrotoxicity of fluoride have been demonstrated in animals, but few studies have examined potential effects in humans. This population-based study examines the relationship between chronic low-level fluoride exposure and kidney and liver function among United States (U.S.) adolescents. This study aimed to evaluate whether greater fluoride exposure is associated with altered kidney and liver parameters among U.S. youth. METHODS This cross-sectional study utilized data from the National Health and Nutrition Examination Survey (2013-2016). We analyzed data from 1983 and 1742 adolescents who had plasma and water fluoride measures respectively and did not have kidney disease. Fluoride was measured in plasma and household tap water. Kidney parameters included estimated glomerular filtration rate (calculated by the original Schwartz formula), serum uric acid, and the urinary albumin to creatinine ratio. Liver parameters were assessed in serum and included alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, blood urea nitrogen, gamma-glutamyl transferase, and albumin. Survey-weighted linear regression examined relationships between fluoride exposure and kidney and liver parameters after covariate adjustment. A Holm-Bonferroni correction accounted for multiple comparisons. RESULTS The average age of adolescents was 15.4 years. Median water and plasma fluoride concentrations were 0.48 mg/L and 0.33 μmol/L respectively. A 1 μmol/L increase in plasma fluoride was associated with a 10.36 mL/min/1.73 m2 lower estimated glomerular filtration rate (95% CI: -17.50, -3.22; p = 0.05), a 0.29 mg/dL higher serum uric acid concentration (95% CI: 0.09, 0.50; p = 0.05), and a 1.29 mg/dL lower blood urea nitrogen concentration (95%CI: -1.87, -0.70; p < 0.001). A 1 mg/L increase in water fluoride was associated with a 0.93 mg/dL lower blood urea nitrogen concentration (95% CI: -1.44, -0.42; p = 0.007). CONCLUSIONS Fluoride exposure may contribute to complex changes in kidney and liver related parameters among U.S. adolescents. As the study is cross-sectional, reverse causality cannot be ruled out; therefore, altered kidney and/or liver function may impact bodily fluoride absorption and metabolic processes.