Is Traffic Pollution Related to Alzheimer’s?

June 02 00:35 2021 Print This Article

A new study suggests that individuals who breathe in traffic-polluted air have a higher likelihood of developing Alzheimer’s disease and other age-related dementia. Published this month by University of California-Davis researchers, the study involved exposing groups of rats to polluted air and filtered air. The rats were exposed to these conditions for 14 months.

Those that were exposed to air polluted by traffic exhibited Alzheimer’s-like gene symptoms similar to those in humans. Exposure also worsened the condition. In other words, the condition got worse for rats that showed genetic risk factors for Alzheimer’s disease.

The researchers said that people can also be at higher risk of developing this disease even if they weren’t genetically predisposed to it. The study showed that exposure to this kind of air can reduce time to the onset of the condition and accelerate it.

Dementia refers to a set of disorders characterized by a change in memory, thinking, and personality, in such a way as to hamper a person’s normal functioning. It affects more than 5 million Americans and 50 million people around the world. This figure is expected to triple by 2050 with prolonged lifespans and aging populations.

People who are aged are at a higher risk of getting dementia. The condition is also connected to family history, race/ethnicity with African Americans being twice as likely and Hispanics 1 and half times more likely to develop the condition than whites.

Other conditions that increase the risk of this disease include high blood pressure, cholesterol, and smoking. Those with traumatic brain injury are also at a higher risk of contracting the disease.

Other studies support this fact

This is not the first time the link between air pollution and dementia is being suggested by studies. The Journal of Alzheimer’s Disease published another review recently, showing this link. The review, which involved 13 published papers, said those exposed to airborne pollutants had a higher risk of dementia condition.

These pollutants include all those found in traffic polluted air carbon monoxide and compounds of nitrogen, and particulate matter.

Need for more studies

Despite these results, experts agree that the studies are far from being conclusive. They are only preliminary. They say these studies do not clearly indicate the relationship between dementia and pollutants. Furthermore, the studies have been conducted on rats and not humans. Hence, real proof can only be found after studies on humans.

Researchers also point to the fact that dementia conditions such as the Alzheimer’s are of a complex nature. For instance, there are many risk factors for these diseases. For this reason, it may be hard to conclude that air pollution can cause them basing on the already carried out studies.

In particular, it is hard to prove a cause-effect relationship using the studies already conducted. However, the studies provide some crucial evidence that proves the strength of association between exposure and dementia.

Real-time exposure to pollution

Critics of these studies say that not one of the studies has faithfully mimicked human exposures. They say that the animals involved in these studies were exposed to very high concentrations of pollutants for a very short period. In contrast, humans are exposed to a subset of components that make the pollution.

However, the new studies may carry some weight concerning showing the strength of association between exposure and results. For instance, the researchers in the newest study said that they exposed animals to ambient traffic-related pollution in real-time over their lifetime.

Both male and female rats were used in the new study. They were exposed to pollution in the busy tunnel in real-time. The pollutants were delivered to the animals directly and unchanged. The first group is rats that expressed human-relevant risk genes for Alzheimer’s disease. The second group had wild-type rats.

More questions than answers

The new study aimed to identify environmental factors that increase the risk for the disease. Researchers said they wanted to determine how traffic-related air pollution affected the aging brain. Of concern is the question of whether both the gases and particulate matter were involved.

Researchers also wanted to establish whether it is pollutants from light or heavy-duty trucks that were more important to causing the disease.

Researchers said they also wanted to use the study to determine whether exposure to traffic-caused air pollution at a young age caused changes that manifested in old age. Or it is just the exposure at mid-late life that exacerbates the risks for the disease. Or whether chronic exposure is important to experience the brain effects.

All these questions are yet to be answered. Thus new studies are needed to help answer them. Likely, these effects will also be worse in children based on new findings from other researchers.

Traffic-related pollution causes other mental issues as well

A USC commissioned study recently found that continued and persistent exposure to traffic-related pollution caused pre-symptomatic signs of cardiovascular disease in children. These signs include stiffening of the arteries. The research has been published in the journal Environmental Health.

The research involved about 5,000 children from kindergarten and first grade and was conducted for one year.

It said that although air pollution was strongly linked to cardiovascular effects in adults, the linkage was not so widely studied in children and young adults. The pollutants have also been linked to hypertensive disorders, especially in children.

Just a month ago, Duke University commissioned a study that said that exposure to air pollution was linked to mental distress and dysfunction at the age of 18.

If found true, it will complicate the use of vehicles and fuels currently being used on roads. It may also increase the calls for the usage of fuel alternatives that have lesser pollution effects. Another effect could be the call for transport alternatives that have lesser polluting effects.

It has already been noted that air pollution has been worsening. More studies have found that outdoor air pollution worsens asthma symptoms. More specifically, traffic-related pollution has been on increase with the increase in vehicle usage. It has also been increasing amidst rising urbanization and population increase.

It is also likely that the effects will be different between urban and rural areas.

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Alan Davison
Alan Davison

Alan Davison, internet researcher, full-time writer for 15 years. Writer and publisher of or Follow me on Twitter.

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