Parabens and Their Effect on Coastal Coral Reefs

Abstract

There is a general concern regarding the extent of harm that the use of cosmetic and pharmaceutical products containing parabens as preservatives can have on coastal coral reefs. There has been little research focused on this study and the results obtained from various lab-based experiments are quite contradictory. Some observed significant damage caused to the reefs by these chemicals while others reported that the concentrations of these parabens were so low that lethal doses could exist in nature. There is evidence of parabens in marine dolphin and fish tissue in accumulated concentration, proving that bioaccumulation can occur in aquatic organisms, and it could happen in coral reefs as well.

In this research, we compared coastal areas with high parabens concentration as these are the regions with high chance of bioaccumulation. Satellite images from NOAA coral reef watch and images from X-Caitlin, accompanied with known concentrations of parabens were used to assess the relationship between high concentration and coral reef bleaching surrounding coastal areas.

From the analysis of satellite data, we observed that the bleaching was mostly temperature driven due to thermal stress, however, regions experiencing similar temperatures, with more swimming activity showed evidence of more bleaching compared to regions with low swimming activity along the same temperature regions. We can therefore conclude that bleaching occurs mostly in regions with high concentration of chemicals as well as thermal stress and these chemicals have a hand in the bleaching experienced by corals around various regions.

Key words: Organic preservatives, parabens, accumulation, bleaching, coral reefs.

Introduction

Parabens are esters of 4-hydroxybenzoic acid. Due to their broad spectrum of antimicrobial activity, they are often used as preservatives in various products in the pharmaceutical, cosmetic and food industry against bacteria, yeast and mold [1-3]. They can be used by themselves or in a combination. Methyl and propyl parabens are the most widely used [4-5]. There is scientific evidence that these chemicals are disruptive to the endocrine system. They are linked to the progression of metabolic disorders like cancer and diabetes [6-8]. Human exposure to these chemicals can lead to oxidative stress that arises due to the presence of excess reactive oxygen species (ROS) which arise when there is an imbalance between the amount produced and the body’s ability to get rid of it after performing their function or recover from the damage they cause to the tissues [9].

Wastewaters collected from hospitals and urban residential areas have a high concentration of parabens because they are used as preservatives in most care products [10-12]. These waters are disposed of at water treatment plants to remove the toxins before being discharged to water bodies. Parabens have moderate solubility in water [13] and therefore, some will be soluble in the aqueous phase at water treatment plants and possibly removed to a great extent. The insoluble parabens will stick to the solid waste and end up in the environment. These could end up in bodies of water when it rains [14]. Additionally, humans use numerous personal care products like oils, lotions and creams which they directly deposit into the oceans when they go swimming [15]. As the parabens are deposited into the water bodies, some will be broken down into various compounds whose toxicity to marine life, mostly to coral reefs is unknown. Others stick to marine sediments or coral reefs and slowly increase in concentration over time. According to the Encyclopedia of the Anthropocene, 70% of all tropical reefs will be destroyed by 2050 [16].

Coral reefs provide a nursery ground for various species of fish. They also protect coastal communities from storm surges, help in water purification; most coral reefs are made up of filter feeder sponges that consume particulate matter that is suspended in water [17-18]. Their absence or decrease in population could lead to an increase in the concentration of particulates and other chemicals that are toxic to the water or marine life [19]. Additionally, since coral reefs have been used in the formation of various anti- cancer drugs and antiviral drugs for HIV, they are and will continue to be front runners in future medicine [20-21]. Maintaining them should be everyone’s priority.

An article published in the America’s Chemical Society’s (ACS) Journal of Environmental Science and Technology reported the appearance of these antimicrobials in marine life. Series of experiments were carried out on various marine organisms from dolphins to smaller fish and amounts of parabens were found in their body tissues. Xue et al. [22] found about 865 ng/g (nanogram/gram) of parabens in livers of bottlenose dolphins from Sarasota Bay, Florida. No significant research has been conclusively conducted to study corals and these antimicrobials. Because coral reefs act as water filters, they can possibly retain a lot of these toxins within and as a result of accumulated concentration; they might be destroyed in big numbers.

Coral reefs are made up of symbiotic organisms that thrive in close proximity with zooxanthellae, which are single-celled symbiotic dinoflagellates [23]. These supply products of photosynthesis needed by the corals as an energy source. This relationship depends on the conditions of the waters they are in. Any changes in water temperature, pH, chemical composition and concentration causes stress to these organisms [24-25]. The zooxanthellae get expelled from their coral host in response to stressful conditions around the coral ecosystem, leaving behind a translucent coral skeleton mainly made of calcium carbonate hence appearing white (bleached) [26].

Preservatives used in the cosmetic industry are washed off into urban wastewaters in concentrations of over 30 μg/L (microgram) and sometimes mg/L [27]. Liao et al [28] collected samples from Korea, Japan and the United States. He determined the concentration of parabens in surface and core sediment samples of sewage samples in Korea. His results showed that parabens in sludge and water sediments had a common source. Vertical profiles showed a gradual increase in the concentration of these chemicals (parabens) in sediments over time. Furthermore, there are reports of accumulation of lipophilic organic UV filters in marine sediments with concentrations measured in hundreds to thousand ng/g dry weight [29]. There is evidence from a few laboratory studies that organic filters can cause coral bleaching. There was a relationship established between the concentration of chemicals and the extent of bleaching. This leads to an assumption that parabens in certain concentrations are stressors to coral reefs.

The purpose of this research is to study the accumulation of parabens in coastal areas by analyzing intergovernmental data and compare it with the proliferation or extinction of the corals.

Methodology

Concentrations of parabens in coastal sea waters obtained from previous research were analyzed alongside satellite images showing bleached areas. This data, along with results obtained from other researchers were compared and conclusions were drawn on the overall impact of parabens on coastal reefs. Data was collected from onsite monitoring databases like X Caitlin global reef record, an organization set up to monitor, collect data and communicate reef science through combining surveys and data from leading ocean researchers. Real time data as well as archived data from the NOAA coral reef watch were also used to study how areas with presumed high parabens concentration were affected, by analysis of the amount of bleaching caused.

The NOAA NESDIS (National Environmental Satellite, Data, and Information Service) visible infrared imaging radiometer suit (VIIRS) was used to detect ocean color (radiance), by estimating the concentration of chlorophyll and the data was used to correlate the relationship between bleaching and presence/absence of chlorophyll.

Figure 1: general structure of parabens.

Figure 2: shows the comparison between healthy and bleached coral reefs Climatechangenews.com

Results and discussion

For a long time, Florida coastal waters have experienced a high concentration of parabens, according to Xue et al. [22]. This indicates a possibility of greater deposition of these chemicals along the coast. Lee et. Al. [27] collected sediment samples along the Korean coastal environments and investigated the contamination status, spatial distribution and potential health risks of these parabens. He found out that both methyl parabens and 4-hydroxybenzoic acid were present in the samples. This was indicative that the extent of contamination did not only stop at the water, the sediments became contaminated as well, showing evidence accumulation.

Figure 1 and 2 show the basic structure of parabens, the bleaching process of coral reefs and the reefs before & after bleaching.

Figure 3, 4 and 5 show satellite images of coral reef bleaching on January 1st, May 1st and August 1st 2019.

From these images, weather changes seem to be the most contributing factor of coral bleaching. However, the images also show that most bleaching occurs in places of high recreational activity, the presence of cosmetic products (like sunscreens, facial as well as body lotions and creams) in such places might play a role in facilitating the bleaching effect of coral reefs. It has been already established that corals get bleached once exposed to unbearable stress [24]. There is also evidence from lab experiments that parabens in certain concentrations provide unfavorable, stressful conditions, leading to bleaching of corals [25]. The concentrations of parabens obtained from water samples were not strong enough to cause bleaching. As already discussed, not all parabens are soluble in water, allowing some parabens to adhere to corals or other sediments. If the researchers were to only take water samples, the results would be faulted as some parabens present would not be accounted for. Therefore, if any form of accumulation were to take place, these concentrations would reach an unbearable level, which could lead to bleaching. Zhao et.al. [26] reported higher accumulation of parabens and their metabolites in concentration higher than those ever reported before in the marine environment. The majority of organisms’ samples taken had potential bioaccumulation evident and the target hazard quotient was higher than 1, which indicated that they had potential to be absorbed into the organism’s body, causing harm.

Figure 6, 7 and 8 show satellite images of ocean color for January 1st, May 1st and August 1st 2019. From this data, we can conclude that there are changes in ocean color throughout the year. Taking the Gulf of Mexico as an example, there is more ocean color in January and as the year progresses to August through May, we see a decrease in ocean color. This is an indication of an increase in coral reef bleaching as the ear progressed through the summer.

Figure 3: Coral reef bleaching for January 1. 2019

Figure 4: Coral reef bleaching for May 1. 2019

Figure 5: Coral reef bleaching for August 1. 2019

Figure 6: Ocean color for January 1. 2019

Figure 7: Ocean color for May 1. 2019

Figure 8: Ocean color for August 1. 2019

Conclusion

From satellite images, one can see that the majority of bleaching occurs during warmer conditions. This leads to inconclusive results as to whether the bleaching was caused by the presence of parabens or by temperature. Deaths of coral reefs are caused by a variety of stressors. These include soaring temperatures, salinity, winds, mechanical factors as well as changes in the chemical and the environment surrounding them. Based on the research obtained from laboratory experiments, parabens can cause bleaching of coral reefs if present beyond a certain concentration. Based on reports of bioaccumulation in fish and dolphin tissue, it can be proposed that this is a result of s the insoluble parabens adhering onto the corals, into sediments or diffusing into the coral reef bodies where they are stored there over time. It is possible the coral and sediments slowly acquire these chemicals in small doses and they accumulate over time and cause catastrophes.

Coral reefs can be restored and as seen from the images, some areas have had lower ocean colors in one year but more color in the following years. This is because most bleaching is caused by environmental factors. Accumulation has yet to cause significant damage but as time goes on, the concentration will go to points of no return, and there will be tremendous coral death.

This study highlights the need to extensively study the effects posed by preservatives used in the cosmetic industry to the environment, most importantly coral reefs. Considering the tremendous advantages that coral reefs give to marine ecosystems, scientists should do their due diligence to analyze how the chemicals in the ocean affect them. Studies should be carried out in situ, on different coral strains for a prolonged period of time because the effects might vary from strain to strain. In most laboratory experiments to study the effects on aquatic corals, the studies are not as realistic as they should be. Sea water and nutrients are added while other conditions are also controlled. However, in real aquatic environments, many conditions cannot be controlled and can therefore fluctuate throughout the year. Lots of effluents and toxins enter the aquatic environment, some of which react with parabens to produce more harmful byproducts that can stay longer in the environment and cause more damage. The experiments should therefore be carried out in conditions as similar to actual aquatic ecosystems as possible in order to draw unquestionable, accurate conclusions.

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