Charles has a deep love for ecology. He enjoys reading about anything related to ecology during his spare time.
The advancement of science and the continual search for a better quality of life by humans have come along with some undesirable effects. Humans have polluted the environment with numerous synthetic organic chemicals to tackle the problems brought about by unwanted organisms such as weeds, insects, rodents, and pathogens. The impact of insecticides like DDT, which was once described as one of life’s great necessities, can still be felt today. Some toxic organic chemicals have even been detected in isolated regions like the Arctic, which goes to show how complex and unpredictable these chemicals can be.
Our ability to recover fossil hydrocarbons from the earth has allowed our society to achieve great technological advances. However, with a global annual production of liquid petroleum products of about 3 billion metric tons, it should come as no surprise that producing, transporting, processing, storing, using, and disposing of organic chemicals have become causes of great concern. Also, synthetic compounds like chlorinated solvents, freons, methyl t-butyl ether (MTBTE), and polychlorinated biphenyls (PCBs) have allowed us to produce products and perform industrial processes with greater efficiencies. These benefits have, however, come at a cost to our environment.
Unexpected and Unconventional Routes
The above processes and activities are the major and conventional ways harmful organic chemicals are produced and distributed into our environment. However, toxic organic chemicals can make their way into our environment through totally unexpected and unconventional routes as well. These compounds can also be formed in the most unlikely of manners, and this goes to show that we still have a long way to go to understand the behaviors of these compounds.
The level at which they are produced in this manner is totally insignificant as compared to the level produced by some well-known industrial processes. However, they have the potential to build up over time in the environment and may rival their conventionally produced counterparts in terms of adverse effects.
- Barbecuing Steaks or Meat Produces Polycyclic Aromatic Hydrocarbons
- Marine Organisms Produce Organohalogens
- Microbial Transformations Produce Phenols
- Water Treatment Produces Aldehydes
- Atmospheric Degradation Produces Halogenated Acetic Acids
1. Barbecuing Steaks or Meat Produces Polycyclic Aromatic Hydrocarbons
Polycyclic aromatic hydrocarbons (PAHs) are mostly introduced into the environment through the combustion of fossil fuels and by direct input of mineral oils. They are one of the major groups of compounds that are of great environmental concern. This is because a good amount of them have been found to be carcinogenic. Also troubling is the fact that some have been found to be persistent and bioaccumulative. This means they have the potential to remain in the environment for a long time and can accumulate in living organisms.
Most people enjoy barbecuing food outdoors, especially during the summer. However, there is strong scientific evidence that PAHs can be formed when barbecuing steaks or other meat. They are produced when fat and juices from meat grilled directly over an open fire drip onto the fire, causing flames. These flames contain PAHs that then adhere to the surface of the meat. PAHs can also be formed during other food preparation processes, such as the smoking of meats.
2. Marine Organisms Produce Organohalogens
Many of the organic chemicals that produce adverse effects in the environment contain one or several halogen atoms, especially chlorine (Cl), and, to a lesser extent, fluorine or Bromine. Halogens are mainly noted for their electronegativity and hence they form strong bonds with carbon which enhances the inertness of a molecule. This is one of the reasons why it is employed in a large number of industrial applications. Its ability to increase the inertness of a molecule also produces the undesirable result of persistence in the environment. Also, halogens tend to make organic chemicals hydrophobic which increases their tendency to partition into organic phases including living organisms. One of the major concerns of organohalogens is their ability to disturb the hormonal balance in living organisms.
Even though the major source of organohalogens is due to direct input by man, they can also be produced naturally. The number of known naturally produced organohalogen has increased in the last decade and it’s as such becoming a cause of great concern. The vast majority of natural organohalogens are produced by marine organisms such as seaweeds, sponges, and corals. They produce these chemicals as defense mechanisms.
3. Microbial Transformations Produce Phenols
Phenolic compounds are important raw materials and additives for a variety of industrial processes. They are used in laboratory processes, chemical industry, plastic processing and so many more. Phenolic compounds have drawn a lot of interest from environmental chemists because some of them have been found to exhibit endocrine-disrupting activities.
Microbes are very important in our environment and carry out transformations of matter essential for life. However, some of these transformations end up producing very harmful products. A prominent example is the formation of 4-nonylphenol from the microbial degradation of 4-nonylphenol polyethylene glycol ethers that are used as nonionic surfactants. This shows that under certain circumstances, microbes are able to transform organic compounds into other organic compounds that are more lethal than the parent compounds. 4-nonylphenol polyethyleneglycol ethers have as such been restricted in many countries because of the ability of certain microbes to transform them into compounds that are of significantly greater concern.
4. Water Treatment Produces Aldehydes
Aldehydes are employed in a wide variety of applications. Some simple aldehydes make suitable solvents for many purposes. This is due to the presence of oxygen in their functional group. Because aldehydes are quite reactive, many important chemical intermediates used in industry exhibit an aldehyde group. Aldehydes have been of great environmental concern because some are known to be carcinogenic. Others have also been found to promote tumor formation.
There is evidence that some potentially dangerous by-products are formed during the water treatment process. This is ironic since our main goal in water treatment is to eliminate any harmful products. Chemicals such as chlorine, chlorine dioxide, and ozone are employed in water treatment for disinfection and destruction of synthetic organic chemicals. However, these chemicals have been discovered to react with the natural organic compound in water and form a variety of simple aldehydes like isobutyraldehyde as by-products.
5. Atmospheric Degradation Produces Halogenated Acetic Acids
Carboxylic acids are very important industrially. They play an important role in the making of soaps, detergents, and plastics. They may be introduced directly into the environment through the use of herbicides such as mecoprop. Halogenated acetic acids are carboxylic acids in which a halogen atom takes the place of a hydrogen atom in acetic acid. Like aldehydes, they can also be formed as by-products during water treatment. Halogenated acetic acids are particularly of great environmental concern. This is because long-term exposure to elevated levels of these compounds may pose a risk in the development of cancer. Also, a high level of exposure to these compounds may increase the risk of birth defects.
The atmosphere is the last place where you would expect toxic environment organic compounds to be formed. However, it has been investigated and confirmed that halogenated acetic acids can be formed from volatile precursors in the atmosphere. For example, there is sufficient evidence that trichloroacetic acid is a minor product of the atmospheric degradation of 1,1,1-trichloroethane and especially tetra-chloroethene. Halogenated acetic acids have as such been detected in high concentrations in rainwater.
Rene P. Schwarzenbach, Philip M. Gschwend, Dieter M. Imboden, V. 1993. An Introduction to Environmental Organic Chemicals. In: Philip M. Gschwend. (ed) Environmental Organic Chemistry. John Wiley and Sons Ltd, United States, pp. 1- 80.
University of Heidelberg. von IJ Fahimi - 2003. Introduction: Halogenated acetic acids.[http://archiv.ub.uni-heidelberg.de/volltextserver/3407/1/DISSERTATIONxxx.PDF] Accessed 8 January 2017.
United StatesEnvironmental Protection Agency. Created in 2002 and updated in December 2009. Persistent Organic Pollutants: A Global Issue, A Global Response. [https://www.epa.gov/international-cooperation/persistent-organic-pollutants-global-issue-global-response] Accessed 8 January 2017.
This content reflects the personal opinions of the author. It is accurate and true to the best of the author’s knowledge and should not be substituted for impartial fact or advice in legal, political, or personal matters.
© 2017 Charles Nuamah