By Jose Jimenez Santiago, member-at-large for the GCI
Over the last four decades, the development of the chemical industry has transformed the global economy and provided a better quality of life for societies worldwide. However, the mass production and disposal of persistent chemicals has been a threat for the environment and the human health. Understanding the effect of chemicals in the environment is necessary in order to replace current harmful molecules with more benign ones1. Fortunately, chemist have learned from negative past experiences and the next generation of chemicals are expected to cause less toxicity and be less environmentally persistent.
Some chemicals have had a negative impact on wildlife populations, some of those effects appear after several years of exposure and bioaccumulation of the toxic molecules in the environment (Figure 1). The first step to prevent further tragedies in wildlife populations is to know the environmental impact of every chemical that is released into the market. However, in places where this data is available, like the United States and Europe, the percentage of chemicals with known environmental information is relatively small. There are around 75, 000 to140, 000 chemicals on the market, out of those, empirical data on persistence is available for only 0.2%, bioconcentration data for only 1% and aquatic toxicity for 11%2,3. Without this information, how can we make an accurate risk assessment of those chemicals? Moreover, molecules with high persistence in the environment may show a negative impact after many years of accumulation. It is important to keep in mind that that for most molecules on the market, we do not know the extent of their negative effects on the environment in the short term and long term2,4.
Figure 1. Examples of wildlife scenarios where chemicals have had or are having population effects 1,6,7,8.
It is hard to shift to a greener chemical industry that prioritizes the environment due to the cost involved in testing the toxicity of molecules. However, there have been advances from the government and chemistry community towards that goal:
- More regulation of chemicals in the environment.
Previously, chemical regulations were targeting the emission of a limited number of pollutants into the environment. New regulations, such as Registration, Evaluation, Authorization and Restriction of Chemicals (REACH2006) in the European Union, are looking to ensure that new chemicals entering the market will conform to minimum human safety and environmental standards5. Thus, manufacturers are responsible for evaluating the impact of new compounds being introduced into the market.
- Analytical development and computer models
Many analytical methods have achieved low limits of detection (LOD). It is now possible to identify all the molecules present in a sample. For example, these methods have been used to analyze urban runoff water and identify unusual pollutants4. With the help of these new, sensitive methods approach it is possible to investigate pollution incidents and identify the industrial location responsible for those incidents.
One major ethical concern when running toxicity tests is the large number of animals needed2. In addition, the many thousands of chemicals yet to be tested make this approach unreasonable. Recently, computer models were used to predict which chemicals will be of greatest concern; namely chemicals which are persistent, bioaccumulative and toxic (PBT). In this survey, out of 95,000 chemicals, only 3-5% were likely to be PBT4. These tolls can make feasible the lab test of the most hazardous chemicals and will reduce the ethical concerns.
- Better wastewater treatment
The incorporation of a secondary biological treatment into wastewater has considerable benefits for the water quality and chemicals reduction. The Activated Sludge Process is the most common method and has been applied in cities all around the world. For example, in China, 81% of the water distributed to the urban population undergoes the Activated Sludge Process9. This shows how we can find cost effective ways to remove chemicals that have accumulated in the environment for many years.
The amount of chemicals used worldwide, their production, diversity, and incorporation has never been greater1. As chemists, it is important to understand the environmental challenges that we face. In addition, chemists should be aware that chemical problems require chemical solutions. We can be pessimistic about the current status of pollutants, but there are tangible reasons to be optimistic about solutions and methods to reduce the negative impact of our current chemical production. Learning from the past is the starting point to ensure that the next generation of chemicals will have less negative impact on the environment.
- Johnson, A.C., Jin, X., Nakada, N., Sumpter, J. P. Science, 2020, 367, 384-387.
- Egeghy, P.P., Judson, R., Ganwal, S., Mosher, S., Smith, D., Vail, J., Cohen Hubal, E. A. Total Environ. 2012, 414, 159-166.
- Judson et al., Environ. Health Perspect. 2009, 117, 685–695.
- Strempel, M. Scheringer, C. A. Ng, K. Hungerbühler, Environ.Sci. Technol. 2012, 46, 5680–5687.
- European Commission, Introduction to REACH regulation, 2019; https://ec.europa.eu/environment/chemicals/reach/reach_en.htm
- P. Desforges et al., Science, 2018, 361, 1373–1376.
- L. Oaks et al., Nature, 2004, 427, 630–633.
- D. Sayer et al., Environ. Sci. Technol. 2006, 40, 5269–5275.
- H. Zhang et al., Environ. Int. 2016, 92–93, 11–22.