Pollution's Impact: Neural Tube Development And Health

Air pollution is a pressing issue that has been linked to various health issues, including an increased risk of neurological disorders and developmental issues. Recent studies have found a correlation between air pollution and neural tube defects (NTDs) in infants. NTDs are birth defects that occur in the brain, spine, or spinal cord of fetuses within the first month of pregnancy, often before the mother is aware of her pregnancy. While the exact cause of NTDs is unknown, it is believed to be a combination of genetic, nutritional, and environmental factors. One such environmental factor is air pollution, with early maternal exposure to high levels of air pollution being linked to an increased risk of NTDs in infants. This adds to the growing body of evidence that suggests a link between air pollution and birth defects, with the specific biological mechanisms still being a subject of research.

Folic acid deficiency

Folic acid, also known as folate, is the natural form of vitamin B-9. It is important for the healthy development of the brain and spinal cord during pregnancy.

Folic acid is provided in the diet, particularly from fruits and vegetables. It is recommended that all people who can become pregnant take 400 micrograms of folic acid every day, in addition to eating folate-rich foods, to help prevent NTDs.

Carbon monoxide exposure

Carbon monoxide (CO) is a colourless, odourless, and tasteless gas produced when fuel like gas, coal, or wood does not burn fully. Exposure to carbon monoxide is dangerous as it reduces the amount of oxygen in the bloodstream, which can lead to unconsciousness and suffocation.

Pregnant women exposed to high levels of carbon monoxide may experience reduced oxygen supply to the baby in the womb, potentially affecting its growth and development. This can lead to severe neurological damage or even fetal death.

A study by Stanford University found a positive correlation between neural tube defects and maternal exposure to carbon monoxide during the first 2 months of pregnancy. Mothers with the highest levels of exposure to carbon monoxide during this period were almost twice as likely to have babies with neural tube defects compared to those with the lowest exposure.

Carbon monoxide poisoning during pregnancy is relatively rare, but it can have serious adverse effects. The severity of fetal complications does not depend on the level of maternal carbon monoxide exposure. Instead, fetal intoxication can be more severe due to the higher affinity of fetal haemoglobin for carbon monoxide, resulting in higher fetal carbon monoxide levels than maternal levels.

To avoid exposure to carbon monoxide, it is important to ensure that household gas and solid fuel appliances are installed and regularly serviced by qualified professionals. Chimneys should be swept regularly, and carbon monoxide alarms should be used to detect any potential issues.

Nitrogen oxide exposure

Additionally, nitrogen dioxide exposure during early pregnancy has been associated with an increased risk of spontaneous abortion. A case-control study in China revealed that elevated levels of nitrogen dioxide exposure during pregnancy were linked to a higher odds of spontaneous abortion, with a 68% increase for every interquartile range increase in exposure.

Overall, nitrogen oxide exposure during pregnancy has been linked to various adverse health effects on the fetus and newborn, including neural tube defects, low birth weight, and an increased risk of spontaneous abortion.

Nitrogen dioxide exposure

Nitrogen dioxide (NO2) is a major air pollutant and a combustion byproduct, often produced at high temperatures. It is a harmful trace species in the Earth's atmosphere.

Effects of Nitrogen Dioxide Exposure During Pregnancy

Short-term exposure to ambient nitrogen dioxide has been associated with an increased risk of spontaneous abortion (SAB). A study in Chongqing, China, found a positive correlation between NO2 exposure and SAB, especially in older women and during cool seasons. Another study in Shanghai, China, revealed that NO2 exposure levels during pregnancy were significantly higher in SAB cases than in healthy controls, suggesting a positive association between NO2 exposure and the risk of SAB.

In addition to the risk of SAB, exposure to NOx and NO2 during the first trimester of pregnancy has been linked to an increased risk of cardiovascular-related malformations in infants, specifically coarctation of the aorta (COA) malformation. A meta-analysis of observational studies found that exposure to NOx and NO2 in the first trimester increased the risk of COA malformation by 13% and 19%, respectively.

Furthermore, a study in California's San Joaquin Valley, an area known for high levels of air pollution, found a correlation between maternal exposure to NO2 during the first two months of pregnancy and neural tube defects in infants. The risk of these defects was almost twice as high for mothers in the highest quartile of exposure to carbon monoxide and 1.7 times higher for those with the highest exposure to NO2.

While the specific mechanisms by which NO2 affects the developing fetus are not fully understood, it is known that NO2 can oxidize tissue composition, increase lipid peroxidation, and inhibit the protective action of the antioxidant defense system, all of which can impact fetal growth and development.

Heavy metal exposure

Sources of Exposure

Heavy metals are commonly found in the environment and in the workplace. They may be ingested through food or water, inhaled as fumes, or absorbed through the skin.

Occupational sources of heavy metal exposure include mining, welding, smelting, and foundry and fabrication work, as well as chemical manufacturing plants that use heavy metals as catalysts.

Types of Heavy Metal Exposure

Heavy metals exist in both inorganic and organic species, with the former being more toxic. The most common heavy metals are:

• Lead
• Mercury
• Cadmium
• Arsenic
• Chromium
• Manganese
• Thallium
• Tin

Effects of Heavy Metal Exposure

• Neurocognitive function impairment
• Cardiovascular diseases
• Cancer
• Developmental abnormalities
• Neurodegenerative diseases

Neural Tube Defects

Neural tube defects (NTDs) are birth defects of the brain, spine, or spinal cord that occur in fetuses within the first month of pregnancy. The two most common NTDs are spina bifida and anencephaly.

Prevention

Folic acid (folate) is important for the fetal development of the brain and spinal cord. A folate deficiency before and during pregnancy increases the risk of having a baby with an NTD.

Treatment

There is no cure for anencephaly or iniencephaly, and infants with these conditions are typically stillborn or die shortly after birth.

Treatment for spina bifida and encephalocele depends on the severity of the condition. Surgery is a common option, and long-term treatment may include multiple surgeries and other treatments related to complications.

Outlook

The nerve damage and loss of function that are present at birth due to NTDs are usually permanent. However, there are a number of treatments that can sometimes prevent further damage and help with complications.

Frequently asked questions