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What are the hazards of formaldehyde?

Time: 2020-07-23

In the present age of the 21st century, most of the citizens of different nations prefer spending time in closed environments especially like shopping malls, indoor restaurants, homes, offices, colleges, etc.

 

There is a high possibility that the amount of unseen pollution particles in closed environments is much higher than the pollution outside of these places.  

 

Generally, the rapid discharge of pollutants is the cause of such kind of indoor pollution.

 

Evaporative and vaporous compounds, also known as volatile organic compounds (VOCs) are radiated by few processes like cooking, combustion, emission of several types of gases, the smoke formed by tobacco, household furniture like bed, tables, chairs, etc. building materials, and traffic pollution.

 

Among all, formaldehyde (HCHO) is one of the most abundant pollutants commonly found in our polluted environment, both in closed and open environments.


What is formaldehyde


Formaldehyde is an uncomplicated chemical compound that is made up of hydrogen, oxygen, and carbon.

 

All life forms including bacteria, plants, fish, animals, and humans naturally generate formaldehyde as a chunk of cell metabolism.

 

Formaldehyde is a chemical that has no color, is flammable, means it can quickly catch fire and has a strong aroma that is used in building materials and to manufacture a lot of daily use items.

 

Formaldehyde is notable for its preservative and germicidal strengths.

 

Other than these features, formaldehyde chemistry is used to produce an extensive range of advanced-level products.

 

It is one of the most studied, researched, and understood compounds in chemical studies.


What are the health effects of formaldehyde


In 1995, the US Environmental Protection Agency (USEPA) recognized indoor environmental contamination as one of the highest environmental threats. 


Formaldehyde was declared as an accepted human carcinogen (cancer causing material) by the International Agency for Research on Cancer and as a predictable human carcinogen by the U.S. Environmental Protection Agency.


1. Researches on formaldehyde


Formaldehyde can provoke irritation of the skin, eyes, nose, and throat, and it has shown to promote cancer in lab test animals.

 

For example: in rats, inhaled formaldehyde was the reason to cause cancers of the nasal cavity and leukemia.

 

In another research, rats were given water having formaldehyde. There was a hike in stomach tumors.

 

Another example of mice was spreading a 10% solution of formaldehyde to the skin was associated with the rapid growth of cancers.

 

An extreme quantity of formaldehyde exposure may originate some types of cancers in humans, but the consequences of exposure to the lesser volume are vague.

 

A study states that if formaldehyde is inhaled at levels of a concentration of 1.9 parts per million (ppm) for 40 minutes, it does not increase blood levels of formaldehyde.

 

Various epidemiology researches of people exposed to formaldehyde in a workstation have a connection between formaldehyde exposure and cancer of the nasopharynx (the upper part of the throat).  

 

Various other researchers have discovered that people associated with the medical occupation, which are using formaldehyde, have greater risks of leukemia.

 

A few studies of industrial members of staff, who are directly exposed to a higher concentration of formaldehyde, have also elevated chances of leukemia.

 

A study discovered that work professionals exposed to formaldehyde had increased levels of chromosome changes in early white blood cells in their bone marrow than normal.

 

This theory reinforces the viable connection between formaldehyde exposure and leukemia. 


2. Higher Formaldehyde levels


Formaldehyde levels are higher in the following three conditions:


  • Homes with smokers:


The smoke made up of burned tobacco holds formaldehyde. If someone smokes tobacco products, then the smoke might be the substantial cause of formaldehyde in their home.


  • Homes with new decoration:


Formaldehyde is often found in the homes /offices which reach from building materials used in the construction.


Especially, pressed wood products, such as particleboard, medium-density fiberboard, and hardwood plywood paneling.


Pressed wood products that use glue, has urea-formaldehyde paste. It normally releases an abundance amount of formaldehyde than those containing phenol-formaldehyde paste.


There will be less and less formaldehyde released as time passes.


But it still needs to take months or even years to stop the emission of formaldehyde completely.


Normally, formaldehyde levels are excessive in newly constructed or newly redecorated homes/offices.


  • Summer Time


In different seasons of the year, the amount of formaldehyde released will vary.


The indoor formaldehyde over-standard rate is 20% in winter, 36% in spring, 84% in summer, and 70% in autumn.


So why does the release of indoor formaldehyde increase in summer?


(1) Temperature:


In summer, the temperature is high, the adhesive has been decomposed, and the decomposed formaldehyde molecules also have enough mobility (absorbing heat energy in the air) to diffuse from the inside of the furniture.


Studies have found that for every 1°C increase in temperature, the volatilized concentration of formaldehyde will increase by 8-12%.


(2) Humidity:


In summer, the humidity is high, and the water molecules are increased and active, which is easily transmitted to the furniture items, causing the adhesive to produce more deliquescence, thereby producing more free formaldehyde.


Related research results show that, when the room temperature rises to 30℃, the relative humidity in the room is 45%, then the released formaldehyde concentration in the air is 0.223mg/m³, which exceeds 2.23 times of the Indoor Air Quality Standard.


When the room temperature rises to 34and the relative humidity is 50%, the release concentration of formaldehyde can exceed the standard 5.53 times.


For every 10°C increase in indoor temperature, the concentration of formaldehyde will approximately double, and the release rate of formaldehyde will double accordingly;


When the indoor temperature rose from 18°C to 38°C, the formaldehyde emission increased from 0.08mg/㎡•h to 0.4mg/㎡•h.


In this environment, people experience symptoms such as eye tingling and itchy throat.


Photodegradation of formaldehyde by photocatalyst TiO2


Formaldehyde (HCHO) is one of the most typical indoor contaminants.

 

Exposure for a longer period of time to the environment with this chemical compound (concentration higher than 0.1 mg/m3) can be hazardous for the human body.

 

Traditional methods for removing formaldehyde (HCHO) from the environment include absorption and dilution with the fresh air and catalysis.

 

Adsorption filter has the restriction of adsorbing saturation and required to be replaced after some time, while dilution with the fresh air has a deficiency of higher energy costs.

 

Photocatalysis is an emerging and encouraging technology for indoor air purification and decontamination using TiO2 as a catalyst under the illumination of UV light.

 

This chemical reaction oxidizes the VOCs into CO2 and H2O at normal room temperature and normal atmospheric pressure.


However, a lot of researches on the degradation of contaminants show that UV/TiO2 alone was not enough in the degradation procedure of gaseous contaminants.

 

When the HCHO is lower than 1ppm, the photocatalytic decomposition of HCHO declined speedily and then almost discontinues on the way.  

 

This is why immobilizing TiO2 on an adsorbent material was used to upgrade and refine the HCHO removal efficiency.

 

Therefore, a TiO2/AC network film was designed by stuffing nanometer particle TiO2 on the surface of activated carbon, in order to eliminate HCHO effectively.

 

The photocatalytic elimination of the gaseous HCHO was carried on the surface of nanometer TiO2 under the irradiation of UV light. During the process,the photo-production holes and electronics can react with the water molecules that adsorb on the catalyst surface to produce hydroxyl.

 

The newly processed hydroxyl is an essential component in the photocatalytic elimination of HCHO. Nanometer TiO2 was used as the photocatalyst.

 

All in all, indoor HCHO can be photocatalytic degraded efficiently by UV light & TiO2/AC network filmand, and can be reduced below 0.1 ppm that is needed by indoor quality standards.

 

It is achievable to photocatalytically degrade indoor HCHO by UV light and TiO2 film.


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