This next common household pollutant might feel obviously harmful to you, but how much do we really know about the insecticides we freely spray to keep cockroaches and other insects away? We are going to explore how knowing which insecticides to use and how to use them in the home is significant to you, the average homemaker.

 

You may recognise some common brands of insecticides in Singapore being mentioned here, including: 

• Baygon (Propoxur)
• Shieldtox (Chlorpyrifos)
• And the notable mention, mothballs (Naphthalene)

 

A quick search in NEA’s document of registered pesticides can tell you what the main active ingredient is in your household insecticide. These chemicals are for general use. This means that while some monitoring is done to make sure the insecticides are sold in acceptable concentrations, there is little regulation on how much is used at each time, and how it is used. The marketing companies are supposed to include usage recommendations on the product packaging by themselves. Despite the fact that household insecticide has become quite commonplace and that we rarely think twice about picking up the insecticide spray, there is actually a lot we do not know about the effects of insecticide use. 

 

First of all, especially in the use of aerosol spray cans, insecticides are released into the air as both water droplets and aerosols. While the water droplets will fall out of the air, the aerosols are tiny enough to be suspended in the air for hours. This is how the chemicals involved can be easily breathed in by unwitting humans (Hill, 2010). Moreover, the aerosols can be unknowingly deposited on the skin and absorbed into the body. Because the aerosols remain suspended in air for quite some time, it does not only affect the insecticide user. Anybody in the household, including children and pets can breathe in the chemicals.

 

Moreover, most of these chemicals (notably propoxur, chlorpyrifos and naphthalene) are semi-volatile organic compounds, which means they can change between matter states rapidly (Hill, 2010). This also makes it a lot easier to breathe in the chemicals unknowingly in their gaseous form. Moreover, the aerosol form of propoxur and chlorpyrifos can persist on surfaces like plush toys and cloth furnishings for up to two weeks (Whyatt, et. al., 2007), meaning that the exposure to the toxic chemicals extends far beyond the spraying of insecticide.

 

Now let us look into the harmful effects of the toxic chemicals themselves. All of these chemicals are at the very least severe irritants, causing irritation to surfaces acutely exposed to the chemical (eyes, skin) and, if breathed in, the lungs. Moreover, there is evidence showing that young children exposed to chlorpyrifos had developmental disorders and slower reflexes (Hu, 2018), and both propoxur and naphthalene are known human carcinogens (National Center for Biotechnology Information, n.d.). 

 

The harm of naphthalene does not just stop there. Naphthalene is a polycyclic aromatic hydrocarbon, which makes them difficult to degrade. The chemical is able to persist for long periods of time in the environment, and when inhaled or ingested, can be bioaccumulated in fat (Hill, 2010). This means that the effects and health risks from the chemical can be magnified with each exposure. This is bad for wildlife as well, as the bioaccumulation of the chemical can cause large health impacts to animals further up the food chain.

 

It seems the exposure to such chemicals should be kept to an absolute minimum where possible. But in the modern household, not using insecticide may seem hard to do. Here are some tips to reduce health risks to yourself and your family members if using insecticides cannot be avoided:

1. Ensure enough ventilation when using insecticides, to allow the outside air to dilute the toxic gas.
2. If possible, place surfaces that have insecticide droplets on them (especially carpets and other fabric surfaces) outside to allow the chemicals to fully evaporate and be blown away.
3. Don’t use mothballs, but if you have to, place them in sealed containers. Only open the containers outside.

 

Author: Alicia Tiu

 

References:

Dich, J., Zahm, S. H., Hanberg, A., & Adami, H. O. (1997). Pesticides and cancer. Cancer causes & control : CCC, 8(3), 420–443. https://doi.org/10.1023/a:1018413522959

Hill, M. (2010). Air pollution. In Understanding Environmental Pollution (pp. 117-154). Cambridge: Cambridge University Press. https://doi.org/10.1017/CBO9780511840654.006

National Center for Biotechnology Information. PubChem Database. Propoxur, CID=4944, https://pubchem.ncbi.nlm.nih.gov/compound/Propoxur (accessed on July 10, 2020)

National Center for Biotechnology Information. PubChem Database. Chlorpyrifos, CID=2730, https://pubchem.ncbi.nlm.nih.gov/compound/Chlorpyrifos (accessed on July 10, 2020)

National Center for Biotechnology Information. PubChem Database. Naphthalene, CID=931, https://pubchem.ncbi.nlm.nih.gov/compound/Naphthalene (accessed on July 10, 2020)

National Environment Agency.  (2019). List of Registered Public Health Pesticide and Repellent Products. Retrieved from  https://www.nea.gov.sg/docs/default-source/default-document-library/approved-list-of-pesticides-(june-2019).pdf (accessed on July 10, 2020)

Whyatt, R. M., Garfinkel, R., Hoepner, L. A., Holmes, D., Borjas, M., Williams, M. K., Reyes, A., Rauh, V., Perera, F. P., & Camann, D. E. (2007). Within- and between-home variability in indoor-air insecticide levels during pregnancy among an inner-city cohort from New York City. Environmental health perspectives, 115(3), 383–389. https://doi.org/10.1289/ehp.9546

Hu, X. (2018, August 26). The Most Widely Used Pesticide, One Year Later. Retrieved from http://sitn.hms.harvard.edu/flash/2018/widely-used-pesticide-one-year-later/ (accessed on July 10, 2020)