Many of us know of the 3 major types of pollution: air, water and land. But, rapid urbanization in the past decades changed our world. There are now other environmental factors we have to contend with. The world, for instance, is a much noisier one now. Gone are the nights of near absolute silence, with you waking up to the sound of that overenthusiastic rooster. Instead, it’s more likely that the noise outside your home never really stopped.
It is just noise. You may think. It shouldn’t be that bad right? Well, think again…
Research shows that prolonged exposure to intense noise levels above 85 dB is likely to have pronounced effects on our health. It can cause a range of health issues ranging from hearing loss, cardiovascular problems, sleep disturbances, unfavorable pregnancy outcomes, cognitive learning disorders to behavioral problems in children.
What is A Safe Noise Level?
Noise refers to all sounds that are undesirable or unpleasant. Sound (or noise) intensity is measured in logarithmic decibel (dB) units. The term “logarithmic” just means that numbers on the scale are not the same distance apart. The decibel scale caters to human audibility.
- Near total silence equates to 0 dB
- A sound 10 times more powerful than that is 10 dB
- A sound 100 times more powerful than near total silence is 20 dB (not 100 dB!)
- A sound 1000 times more powerful than near total silence is 30 dB
- … and so on…
The higher the decibel level, the louder the noise, and the more damage to your hearing!
The safe limit recommended by experts at the US Environment Protection Agency is 70 dB. Below this level, even prolonged exposure is unlikely to cause hearing loss. But, many of us are exposed to much greater intensities on a daily basis. Any level at or above 85 dB is likely to cause damage over time. The louder the sound, the shorter the amount of time is needed to cause damage.
Health Effects of Noise Pollution
According to the World Health Organisation (WHO), exposure to excessive noise is the 2nd major cause of adult-onset hearing loss. This is largely preventable. Excessive noise can overstimulate and damage the sensory cells of the inner ear.
Hearing loss can occur either gradually or suddenly, depending on how long and how loud the noise. Victims often first notice having problems understanding speech in noisy situations. These difficulties can be worse in fluctuating noise. Over time, challenges in interacting with others may lead to social isolation.
Besides, hearing loss due to noise exposure can predispose you to tinnitus. Tinnitus refers to the experience of detecting sound when it is in fact absent. This happens when the central nervous system is faulty and sends false signals to the brain. Why does it do that?
When there is a stimulus (such as sound), the nearest sensory cell that experiences it gets excited. This excited sensory cell fires signals to the nerve cell right next to it, which then “passes the message” closer and closer to the brain. Now think of this signaling as a long chain of people holding hands. The first person reacts to the stimulus and squeezes the next person’s hand to pass the message. Eventually the message is received by the last person (the brain). Squeezing stops when there is no more stimulus to excite the first person. But, imagine if the stimulation was excessive. Some people may be so used to squeezing hands, they forget to stop – even when the stimulus is long gone!
People who suffer from tinnitus describe hearing “ringing”, “buzzing”, “whistling” and other noises. Tinnitus can reduce our ability to concentrate and relax. A frequent sequelae is the development of anxiety and depression.
Long-term noise exposure may also increase risk for noise sensitivity. If severe, this condition can be highly debilitating in our noisy world.
The cardiovascular system is also known as the circulatory system. It consists of the heart and a closed system of blood vessels. The heart is an incredible muscle that pumps blood to the entire body, supplying all its parts with nutrients and helping with the removal of waste.
But, this self-regulating system is not immune to the threats from our environment. Scientists have found links between noise exposure and cardiovascular disease. They suggest that acute noise exposure can
- Increase blood pressure
- Change our heart rate
- Release stress hormones
Chronic noise exposure further results in
- Higher blood lipid concentrations
- Higher blood viscosity
- Higher blood glucose concentrations
These can put a strain on the cardiovascular system, resulting in risk of hypertension and atherosclerosis. More severe events like heart attack and stroke tend to occur with these risk factors.
Unfavorable Pregnancy Outcomes
Pregnancy is one of nature’s most amazing feats. It also places a lot of stress on the mother’s body, with all that growing happening at breakneck speed! Researchers looked at nearly 270,000 deliveries in Canada. Their finding? Women exposed to environmental noise pollution had a higher risk of preeclampsia. This is a pregnancy complication that can lead to maternal and infant death if untreated. Signs include hypertension and damage to another organ system (usually liver and kidneys). Poorer blood flow to the placenta also may lead to preterm births and smaller babies. It is only logical to cut as many risk factors as possible. We need to protect mothers and their babies during this vulnerable time.
While sleeping, our conscious minds are rarely fully aware of our external environment. But that does not mean that our physical bodies are equally unperturbed. Our bodies continuously experience, evaluate and react to environmental sounds (even if we are not aware of it). Awakenings are relatively rare in most people, because sleep is “actively protected” by our bodies. Most of us are able to adapt quickly to new noises and new sleeping environments. But, the physiological reactions do not adapt. This is demonstrated by effects such as changes to heart rate and increased motility.
Nature provided us with some safeguards to ensure we sleep. But, sleep can still be disturbed if noise levels exceed a certain threshold.
The WHO came up with a summary of effects and threshold levels for effects. It recommends that sound levels be kept at a maximum of 40 dB for the long-term prevention of noise-induced health effects during sleep.
Poor sleep is known to result in a whole host of downstream effects. Reversible, short-term effects include sleepiness and moodiness. But these can morph to more dangerous problems such as depression and violence. And it doesn’t just affect you. If noise is affecting your home, your loved ones will be affected too. Imagine a bunch of irritable and sub optimally-functioning humans living under 1 roof!
This table by Lavie, Pillar and Malhotra (2002) summarizes the other effects of poor sleep.
|Short-term Consequence||Long-term Consequences|
|Cognitive||Impairment of function||Difficulty learning new skills|
Short-term memory problems
Difficulty with complex tasks
Slow reaction time
|Neurological||Mild and quickly reversible effects||Cerebellar ataxia|
Increased sensitivity to pain
|Others||Impairment of immune function||Susceptibility to illness|
Cognitive and Learning Disorders
Children may be particularly vulnerable to their environment. This may be because they cannot articulate discomfort well. Their relatively small size also means they are more heavily exposed to pollutants in proportion to their body weight. Thus, there is keen interest to investigate the effect of various pollutants on this at risk group.
Researchers looked at close to 3000 European school children who attend schools near major airports. The inevitable chronic plane noises were found to impair cognitive development. Many of these children had greater difficulty gaining knowledge and problem solving skills. Reading comprehension, in particular, was challenging. Another study conducted in the UK also found that children fared poorer in similar environments. These children had poorer recognition memory, conceptual recall memory and information recall memory. In all, more than 20 studies found that places with high noise levels are not conducive for learning.
Hyperactivity refers to continuous activity, impulsiveness, difficulty concentrating, aggressiveness and being distracted easily. Other typical hyperactive behaviours include fidgeting, wandering and talking too much. Children who live near airports in the Netherlands, Spain and UK were found to be more hyperactive. In Germany, road traffic noise exposure in 10 year olds also caused hyperactivity.
In Asia, close to 1000 elementary and middle-school children in South Korea were evaluated. It was found that noise was associated with behavioural problems. With higher noise exposure, parents reported that their children displayed more:
- Aggressive behavior
- Anxious / depressed behaviour
- Attention Problems
- Rule-breaking behavior
- Somatic complaints
- Social problems
- Thought problems
- Withdrawal / depression
These behavioral issues in children do not end with childhood or the adolescent years. Such children usually have poorer social skills, self-confidence, and poorer relationships with peers. There could be long-term implications for educational achievement and occupational opportunities as adults. And that is a compelling reason to nip such problems in the bud!
It’s hard to imagine that noise can have such an effect on our health, well-being and lives. Noise pollution crept up on us insidiously. It also doesn’t help that we cannot “see” noise. But let’s imagine for a minute that every sound you hear right now is a piece of garbage. How large is that garbage pile around you? It’s time to get to work clearing the trash!