Linking environmental exposure and effects of pharmaceuticals on aquatic biota: state of knowledge in Latin America

Human PhACs in fresh surface water

Based on the research conducted [n = 44 articles; Supplementary Table 2], most of the reported concentrations (= 99%) were in the same order of magnitude as those previously reported for fresh surface waters worldwide (< 40,000 ng/L)^[10,14]. Specifically, 113 PhACs belonging to 26 different therapeutic groups have been reported in fresh surface water from Latin America. Among these therapeutic groups, 21 PhACs belong to psychiatric drugs, 17 to analgesics/anti-inflammatories and 16 to antibiotics [Table 1, Supplementary Table 2]. The group with the highest observed concentrations (0.1-227,000 ng/L) were analgesics/anti-inflammatories [Figures 1 and 2], as previously reported in North America, Europe, South Africa, and Australia^[9,14,29]. This therapeutic group includes non-steroidal compounds (e.g., acetylsalicylic acid, acetaminophen, ibuprofen), which are mostly used as painkillers and sold in large quantities, usually without prescription. Specifically in Latin America, the highest concentrations of analgesics/anti-inflammatories belong to acetaminophen and have been reported in Brazil (30,421 ng/L)^[30] and Bolivia (227,000 ng/L)^[10]. However, this last report from Bolivia appears to be an outlier, as it is three orders of magnitude higher than the maximum concentration reported for North America (291 ng/L) and Europe (394 ng/L)^[10], and it is the only value of this magnitude in Latin America [Supplementary Table 2]. Although the octanol-water partition coefficient of acetaminophen indicates low lipophilicity (log K_ow = 0.9), as with most analgesics, its ionizability depends on the pH of the environment, which can greatly alter this value^[11]. According to the authors' descriptions, the site in Bolivia (Seke River) is suspected of draining septic tanks and the site in Brazil (Água Quente stream) is the main receptor of untreated wastewater. In addition, the authors who reported the high concentration in Brazil linked it to nonprescription sales and widespread consumption of analgesics. However, the problem of nonprescription sales is not unique to this country but is widespread throughout Latin America. Thus, the characteristics of each location could be the reasons for the higher concentrations. In this sense, comparisons between measurements performed in different countries should be made with caution to avoid false conclusions. In other words: in this review, we could compare each concentration with poverty level and access to health care, age structure, degree of urbanization or even per capita income. However, the measurements were made using different analytical methods, in different environments (rivers, streams, ponds) and at different times of the year. Therefore, this review aims to provide an overview of PhACs contamination of fresh surface water from Latin America through general comparisons at the regional level and by weighing the knowledge gaps.

Figure 1. Maximum concentrations of human pharmaceutically active compounds reported in fresh surface water from Latin America.

Figure 2. Total concentrations of human pharmaceutically active compounds, classified by therapeutic group, reported in fresh surface waters from different Latin American countries.

Another therapeutic group with high concentrations was stimulants/lifestyle [Figure 2], consisting mainly of caffeine (2.0-129,585 ng/L). This result makes sense considering that caffeine is used in combination with other groups that also showed high concentrations in the environment. Besides, its uptake with drinks and foods caused its inclusion on the U.S. EPA list of High Production Volume Chemicals. For all these reasons, it is usually considered as an anthropogenic marker in aquatic systems, but mainly because it is ubiquitous in surface water, seawater and also groundwater^[14,31]. Here, we demonstrated that there is a significant association between the mean concentration of PhACs in fresh surface waters and the mean concentration of caffeine at different sites in Latin America [Supplementary Figure 1]. The range of concentrations of this compound in rivers and lakes from North America (3-1440 ng/L) and Europe (50-2,400 ng/L) is similar to the range reported for Latin America, except for two outliers from Brazil (129,585 ng/L^[30] and 127,092 ng/L^[32]) [Figure 2]. Antidiabetics (1.50-64,100 ng/L) and psychiatric drugs (0.04 ng/L-36,920 ng/L) are the other two therapeutic groups that showed high concentrations [Figure 2], with metformin and carbamazepine leading in each of these groups. Metformin is a compound that appears to act directly or indirectly on the insulin receptor. The maximum concentration measured in surface waters in the United States was 150 ng/L^[33], two orders of magnitude lower than in Latin America. Carbamazepine is used primarily for the treatment of epilepsy but also as a psychotropic drug. The range of concentrations in surface waters from North America, Europe, South Africa, and China (0.2-11.600 ng/L)^[14] is similar to the range reported for Latin America, with the exception of an outlier from Colombia (36,920 ng/L)^[34].

Another therapeutic group that deserves special mention is that of antibiotics, which includes all natural or synthetic compounds that have a selective toxic effect on bacteria or other unicellular microorganisms^[11]. It consists of a very large group of compounds with different physicochemical properties that have been detected in surface waters from Latin America [0.6-25,000 ng/L, Figures 1 and 2] at lower concentrations than the previous therapeutic groups, as found in North America (30-1,900 ng/L)^[33,35], Europe (0.5-29,000 ng/L)^[9,36,37] and Africa (34-21,000)^[9]. Among this therapeutic group, the higher concentrations for Latin America belong to clarithromycin (3-25,000 ng/L)^[38,39], sulfamethoxazole (5-6,550 ng/L)^[10,40], and trimethoprim (2-3,580 ng/L)^[10,34]. The maximum concentration of clarithromycin is one or two orders of magnitude higher than those reported for North America (857 ng/L), Europe (186 ng/L), Asia (177 ng/L), and Africa (241 ng/L)^[10]. The same is true when comparing the maximum concentration of trimethoprim reported for Latin America with the values reported in North America (61 ng/L), Europe (36 ng/L), Asia (44 ng/L), and Africa (287 ng/L)^[10]. For sulfamethoxazole, the maximum concentration is an order of magnitude higher than the levels reported for North America (111 ng/L) and Asia (200 ng/L)^[10]. The estimated supply of over-the-counter antibiotics is 62% worldwide, which corresponds to 65% for Asia, 53% for Southern and Eastern Europe, 57% for Africa, and 78% for South America^[41]. However, it would be inappropriate to associate the high concentrations of antibiotics in Latin America with better access to over-the-counter antibiotics for two reasons: 1: the range of antibiotic concentrations found in the region is similar to other regions of the world, as mentioned earlier, 2: the article from which this percentage was estimated for Latin America is based on data from only 3 countries (representing less than 1% of the region). Therefore, more variables need to be evaluated to determine the reasons why some PhACs are detected at higher concentrations than others.

Looking at the 33 countries in Latin America, concentrations of PhACs in fresh surface water were registered in less than 40% of them, with Brazil (24 papers quantifying 47 different compounds), Argentina (10 papers quantifying 56 different compounds and 20 unpublished new compounds) and Mexico (5 papers quantifying 24 different compounds) topping the list [Figures 1 and 2]. Concentrations greater than 2500 ng/L were detected in all countries where PhACs were measured (n = 12), but only seven of them had concentrations greater than 5000 ng/L. Although investment in research and development in this region has steadily increased in recent years, only three countries account for 88% (Brazil = 64%, Mexico = 17%, and Argentina = 7%)^[42]. Thus, the lack of studies in the region seems to be related to the lack of government support.

The largest number of PhACs was reported in Argentina (n = 76). However, it should be noted that this number includes 20 new PhACs recently reported in an unpublished research article^[43] by one of the authors of this review. However, ignoring this article, Argentina still tops the list (n = 56), although the number of PhACs reported in Brazil is not so different (n = 47). In other words, Argentina and Brazil are the countries with the most reported PhACs. However, when considering the number of articles published in each country, the number in Brazil is two times higher than that in Argentina. This is probably due not only to the analytical capabilities of each country, but also to the objectives of each study. It should also be noted that in Argentina, all measurements were made in the central region of the country, whereas in Brazil, measurements were scattered throughout the national territory. Both patterns are consistent with the concentration of urban areas in each of these countries. Therefore, it is necessary to increase the number of sampling sites to perform measurements in different regions of each country.

Human PhACs accumulated in aquatic biota

Based on the research conducted [n = 8 articles; Supplementary Table 2], all reported concentrations were in the same order of magnitude as most of the previously reported concentrations for aquatic biota worldwide (< 1,000 ng/g d.w.)^[44]. Although the highest concentrations are generally found in waters adjacent to areas with direct discharge of treated municipal water or areas with significant water runoff from highly urbanized and populated areas, bioaccumulation has been found in freshwater biota from areas distant from the source of contamination^[44,45]. This makes sense because concentrations in aquatic biota are the result of daily and historical exposure to bioavailable PhACs in surface water. In this sense, bioaccumulation is determined by the absorption, distribution, metabolism and excretion capacity of aquatic organisms, in addition to their migration capacity. This raises questions about transportation pathways and persistence of pharmaceuticals in terms of global environmental health risk^[44].

In Latin America, 57 PhACs belonging to 18 different therapeutic groups have been reported in aquatic biota. Of these therapeutic groups, 13 PhACs belong to psychiatric drugs, 10 to antibiotics and 8 to analgesics/anti-inflammatories [Table 1, Supplementary Table 2]. The highest reported concentrations belong to antibiotics bioaccumulated in biofilm (5-652 ng/g d.w.)^[39,46] and vascular plants (20-112 ng/g d.w.)^[46] [Figures 3 and 4]. The antibiotic with the highest concentration was ciprofloxacin (400-652 ng/g d.w. in biofilm)^[39] (log K_ow = 0.28), as previously reported for cultured and wild organisms^[11]. However, the highest concentrations reported in China (3-4 ng/g d.w. in fish muscle and decapods)^[44] are two orders of magnitude lower than those reported in Latin America. Thus, the fate and distribution of antibiotics in the environment may depend on other factors and not only on the K_ow value, which is considered a good predictor of the bioaccumulative capacity of most compounds. That is, the K_ow value is only a chemical property that does not take into account biological and environmental factors such as bioavailability and biotransformation, and it is expected to give many false positives for ionizable polar organics^[47]. Another issue to consider is the definition of bioaccumulation, as most studies consider chemical concentrations in an organism that exceed those found in the respiratory medium and the diet^[47], whereas some studies refer to the concentration of a compound within cells and in the surrounding matrix^[39]. The latter definition has been used to describe the bioaccumulation of antibiotics in biofilm, which may explain the higher concentrations reported.

Figure 3. Maximum concentrations of human pharmaceutically active compounds bioaccumulated in aquatic biota from Latin America.

Figure 4. Total concentrations of human pharmaceutically active compounds, classified by therapeutic group, reported in aquatic biota from different Latin American countries.

Another therapeutic group with high concentrations were analgesics/anti-inflammatories [0.1 ng/g - 163 ng/g d.w., Figure 4], with codeine (163 ng/g d.w. in whole fish)^[48], acetaminophen (~80 ng/g d.w. in anuran muscle)^[43] and ibuprofen (63 ng/g d.w. in biofilm)^[46] leading the group. Of these three PhACs, acetaminophen was the only one whose concentration was two orders of magnitude higher in North America (4,660 ng/g d.w. in fish plasma)^[49] than in Latin America. However, the fact that the report was made in plasma could explain the difference in magnitude in terms of tissue accumulation.

Psychiatric drugs (1-90.8 ng/g d.w.) and β-Blocking agents (1-85 ng/g d.w.) were the other two therapeutic groups that showed high concentrations [Figure 4]. For each of these groups, carbamazepine (90.8 ng/g d.w. in fish muscle)^[50] and propranolol (85 ng/g d.w. in whole fish)^[48] showed the highest concentrations. Notably, psychiatric drugs were the only group reported in all Latin American countries where bioaccumulation studies were conducted. However, as with fresh surface waters, we hypothesize that the lack of reports is related to the lack of government support for conducting studies rather than the actual presence/absence of a particular PhAC in the environment. Among β-Blocking agents, the concentration of propranolol reported for Latin America is two orders of magnitude higher than that reported for Canada (8.3 ng/g w.w. in bivalves)^[51].

At the regional level, only 12% (n = 4) of countries recorded concentrations of bioaccumulated PhACs in aquatic biota, with fish being the most studied taxonomic group. Besides, analgesics/anti-inflammatories were reported only in Argentina and Uruguay, and most of the reports of other therapeutic groups were made in Argentina, showing the lack of field studies with wildlife [Figure 3]. That is, Argentina is the Latin American country with the most reported PhACs in aquatic biota, both considering (n = 55) and not considering (n = 34) the previously mentioned unpublished work^[43]. Therefore, future studies should be conducted to better understand the range of concentrations of each PhAC and therapeutic group in the region.

Effects of PhACs on aquatic biota

Based on the research conducted, we found 67 no observed effect concentration (NOEC) values for 37 PhACs, 36 lowest observed effect concentration (LOEC) values for 26 PhACs and 45 lethal concentration (LC50) values for 31 PhACs [Supplementary Table 3]. Considering the PhACs for which we found reports in fresh surface water, less than half (50 out of 113) were tested in the laboratory for lethal or sublethal effects on an aquatic organism. Lethal and sublethal effects of most PhACs were evaluated in fish (n = 45) and crustaceans (n = 32), with amphibians (n = 15) and algae (n = 12) being the groups with the least available information [Figure 5]. Looking at the targets for prioritization of compounds, based on the available information, those compounds whose highest environmental concentrations exceed the lowest reported LC50 should be prioritized (high prioritization), followed by those whose highest environmental concentrations exceed the lowest reported LOEC (medium prioritization), and finally, those whose highest environmental concentrations exceed the lowest reported NOEC values (low prioritization). That is, the order of prioritization would be from right to left in the analysis of Figure 5. Specifically, the only compound whose concentration in fresh surface water exceeded the minimum lethal concentration was acetaminophen (lowest LC50 in crustaceans = 32,000 ng/L^[52]). Regardless of whether this concentration in water is an outlier value, this is an alarm signal for the need to continue monitoring concentrations of this PhAC in water because of its potential to cause lethal effects. Also, there are several other PhACs for which the reported maximum concentration in fresh surface water exceeds the NOEC (n = 13 out of 33) and/or LOEC (n = 11 out of 20). Specifically, acetaminophen (analgesics/anti-inflammatories), caffeine (stimulants/lifestyle), carbamazepine (psychiatric drugs), propranolol (β-blocking agents), 17α-ethinylestradiol and 17β-estradiol (Estrogens) were the only six PhACs whose NOEC and also their LOEC values were lower than the concentration in fresh surface water [Figure 5]. Therefore, special attention should also be paid to these PhACs. In view of the above, the information available worldwide on the ecotoxicology of PhACs is still scarce [Table 1].

Figure 5. Comparison of the maximum concentration of different pharmaceutically active compounds (PhACs) reported in fresh surface waters from Latin America with the lowest concentrations of each PhAC that induced no effects (NOEC) or sublethal/lethal effects (LOEC, LC50) in laboratory tests with algae, crustaceans, amphibians or fish. W > E: water concentration exceeding at least one NOEC, LOEC, or LC50