Levels of Arsenic, Cadmium, and Mercury in Urine of Indigenous People Living Close to Oil Extraction Areas in the Peruvian Amazon

Vol. 131, No. 5 Research LetterOpen AccessLevels of Arsenic, Cadmium, and Mercury in Urine of Indigenous People Living Close to Oil Extraction Areas in the Peruvian Amazon Cristina O’Callaghan-Gordo, Jaime Rosales, Pilar Lizárraga, Frederica Barclay, Tami Okamoto, Diana M. Papoulias, Ana Espinosa, Martí Orta-Martinez, Manolis Kogevinas, and John Astete Cristina O’Callaghan-Gordo Address correspondence to Cristina O’Callaghan-Gordo. Email: E-mail Address: [email protected] https://orcid.org/0000-0002-4229-2991 Faculty of Health Sciences, Universitat Oberta de Catalunya, Barcelona, Spain ISGlobal, Barcelona, Spain Universitat Pompeu Fabra, Barcelona, Spain CIBER Epidemiología y Salud Pública, Spain Search for more papers by this author , Jaime Rosales Centro Nacional de Salud Ocupacional y Protección del Ambiente para la Salud, Instituto Nacional de Salud, Lima, Peru Search for more papers by this author , Pilar Lizárraga Centro Nacional de Salud Ocupacional y Protección del Ambiente para la Salud, Instituto Nacional de Salud, Lima, Peru Search for more papers by this author , Frederica Barclay Centro de Políticas Públicas y Derechos Humanos–Perú Equidad, Lima, Peru Search for more papers by this author , Tami Okamoto Department of Geography, University of Cambridge, Cambridge, UK Search for more papers by this author , Diana M. Papoulias E-Tech International, El Sobrante, California, USA Search for more papers by this author , Ana Espinosa ISGlobal, Barcelona, Spain Universitat Pompeu Fabra, Barcelona, Spain CIBER Epidemiología y Salud Pública, Spain Hospital del Mar Medical Research Institute, Barcelona, Spain Search for more papers by this author , Martí Orta-Martinez Department of Evolutionary Biology, Ecology and Environmental Sciences, Faculty of Biology, University of Barcelona, Barcelona, Spain Search for more papers by this author , Manolis Kogevinas ISGlobal, Barcelona, Spain Universitat Pompeu Fabra, Barcelona, Spain CIBER Epidemiología y Salud Pública, Spain Hospital del Mar Medical Research Institute, Barcelona, Spain Search for more papers by this author , and John Astete Centro Nacional de Salud Ocupacional y Protección del Ambiente para la Salud, Instituto Nacional de Salud, Lima, Peru Search for more papers by this author Published:3 May 2023CID: 057701https://doi.org/10.1289/EHP11932AboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InReddit IntroductionOil extraction can lead to long-term harm to the environment and human communities.1 In the 1970’s, oil extraction started in the northern Peruvian Amazon, in the Corrientes, Pastaza, and Tigre river basins, all major tributaries of the Marañón River, leading to high levels of environmental contamination in these four river basins. The oil concessions of this area, which are currently among of the most contaminated areas of the country [see reports on oil Blocks 8 and 192 (formerly 1AB)], overlap with the territories of the Achuar, Quechua, Kichwa, and Kukama Peoples. These Indigenous groups belong to the Jivaro, Quechua, and Tupi linguistic families, respectively. They live in the northern Amazon, on the border between Peru and Ecuador. According to the 2017 Peruvian National Census (indigenous communities module), it is estimated that approximately 7,944∼7,944 Achuar, 11,347 Quechua, 4,742 Kichwa, and 9,532 Kukama Peoples live in these four river basins.2 These groups were mostly nomadic-hunter gatherers until the 1960s when they settled in small communities. Nowadays, they continue to rely on subsistence agriculture and on hunting and fishing for their daily protein intake. Since the arrival of the oil companies to the area, the inhabitants of the area have shown concerns about the potential health effects of the environmental contamination caused in the area. High blood lead levels (greater than 5 micrograms per deciliter>5μg/dL in 49% of children and in 60% of adults) were reported among the population of these river basins,3 but there is no information on other metals. The primary aim of this study was to estimate concentrations of metals in urine of Indigenous People residing in four major river basins in oil concessions areas in Peru. Associations were then explored between previously reported urinary metal concentrations and sociodemographic, environmental, occupational, and lifestyle factors.MethodsWe conducted a cross-sectional study and assessed urinary concentrations of total arsenic (U-As), cadmium (U-Cd) and total mercury (U-Hg) in the populations of the Corrientes, Pastaza, Tigre, and Marañón River basins (Figure 1) in collaboration with indigenous federations from the northern Peruvian Amazon (ACODECOSPAT, FECONACOR, OPIKAFPE, FEDIQUEP, PUINAMUDT) in May–June 2016. The study design was described in detail elsewhere.3 Briefly, we followed a two-stage stratified random strategy to select study participants. Thirty-nine communities were selected and between 14% and 15% of families were randomly selected in each community. Participation was offered to all members of the selected families, excluding infants under 6 months of age. The study protocol was reviewed and accepted by the Ethics and Research Committee of the National Institute of Health (NIH), Peru. Written informed consent was given from traditional leaders to conduct the study in each of the communities. Participants greater than or equal to 18≥18 years of age provided written informed consent, and participants between greater than or equal to 7≥7 and less than 18<18 years of age provided personal verbal consent and their parents provided informed written consent. For participants less than 7<7 years of age parents provided informed written consent.Figure 1. Map of the study area. Block 1AB/192 and Block 8 refer to the two oil concessions areas that overlap with the territories of the Achuar, Quechua, Kichwa, and Kukama Peoples in the Corrientes, Pastaza, and Tigre river basins of the northern Peruvian Amazon. Central processing facilities include production facilities where oil, gas, and produced water are collected from the oilfield and separated, as well as storage tanks, flare systems, utilities, and support buildings. The figure was elaborated using ArcGIS Pro (version 2.5.0; ESRI) and open-access spatial data on oil concessions and infrastructure, indigenous communities, and natural protected areas.Face-to-face questionnaires were administered to the heads of households to collect information on dwelling and to all family members to collect information on individual risk factors. Urine samples were collected, preserved, and analyzed by atomic absorption spectrophotometry following protocols validated by the Peruvian NIH.4 The limits of detection (LODs) were 2.5 micrograms per liter2.5μg/L for U-As and U-Hg and 0.5 microgram per liter0.5μg/L for U-Cd. We replaced metal values below the LOD by the LOD divided by 2. Thirty-two percent (266), 31% (259), and 50% (408) of measurements were below the LOD for U-As, U-Hg, and U-Cd, respectively.We used linear regression models of log-transformed variables, taking into account the multilevel study design.3 Results were back-transformed and presented as geometric mean ratios with 95% confidence intervals [GMR (95% CI)], stratified by age using a threshold of 12 years of age. Associations were tested using the Wald test, and variables associated in individual models (lowercase italic p less than 0.1p<0.1) were considered in multiple regression models. If multicollinearity was observed (variable inflation factors greater than 5>5), we dropped one of the correlated variables from the model. All analyses were made using Stata (version 14; StataCorp). The map in Figure 1 was elaborated using ArcGIS Pro (version 2.5.0; ESRI) and open-access spatial data on oil concessions and infrastructure, indigenous communities, and natural protected areas.Results and DiscussionCreatinine-corrected concentrations of metals were available for 824 participants, of which 230 were children (less than 12<12 years of age) and 594 were adults (greater than or equal to 12≥12 years of age). Characteristics are presented in Table 1. Average concentrations of U-Hg were 4.1 micrograms per gram4.1μg/g for children and 4.4 micrograms per gram4.4μg/g for adults. Corresponding concentrations for U-As were 27.7 micrograms per gram27.7μg/g and 15 micrograms per gram15μg/g, and for U-Cd 0.8 microgram per gram0.8μg/g and 1.1 micrograms per gram1.1μg/g. Twenty-five percent (lowercase italic n equals 57n=57) of children and 28% (164) of adults had U-Hg levels above reference values (RVs) established by the Peruvian Ministry of Health (MINSA) (5 micrograms per gram5μg/g). For U-As, the corresponding percentages (reference value equals 20 micrograms per gramRV=20μg/g) above the RV were 48% (110) for children and 23% (135) for adults, and for U-Cd (reference value equals 2 micrograms per gramRV=2μg/g), 2% (6) and 13% (76), respectively.Table 1 Urine creatinine-corrected concentrations (micrograms per gramμg/g) of total arsenic (As), cadmium (Cd), and total mercury (Hg) and associations with sociodemographic, lifestyle, environmental, and occupational exposures by age group among Indigenous People living close to oil extraction areas in the Peruvian Amazon, May–June 2016 (230 participants less than 12<12 y old; 594 participants greater than or equal to 12≥12 y old).CategoryStudy populationAsCdHgless than 12<12 ygreater than or equal to 12≥12 yless than 12<12 ygreater than or equal to 12≥12 yless than 12<12 ygreater than or equal to 12≥12 yless than 12<12 ygreater than or equal to 12≥12 yN (%) or mean plus or minus SDmean±SDN (%) or mean plus or minus SDmean±SDGM (95% CI)GMR (95% CI)p-ValueGM (95% CI)GMR (95% CI)p-ValueGM (95% CI)GMR (95% CI)p-ValueGM (95% CI)GMR (95% CI)p-ValueGM (95% CI)GMR (95% CI)p-ValueGM (95% CI)GMR (95% CI)p-ValueAge (y)a7.3 plus or minus 2.77.3±2.736.3 plus or minus 16.336.3±16.3—0.93 (0.89, 0.98)0.008—0.99 (0.99, 1.00)0.008—0.99 (0.96, 1.03)0.608—1.02 (1.01, 1.02)less than 0.001<0.001—0.98 (0.94, 1.02)0.304—1.01 (1.00, 1.01)0.001Sexb Female119 (51.7)331 (55.7)15.1 (12.6, 0.98)Ref—10.9 (9.9, 12.0)Ref—0.6 (0.5, 0.7)Ref—0.9 (0.8, 1.0)Ref—3.2 (2.8, 3.7)Ref—3.1 (2.9, 3.4)Ref— Male111 (48.3)263 (44.3)20.8 (17.6, 24.7)1.35 (1.08, 1.70)0.01310.0 (9.1, 11.0) 0.99 (0.88, 1.11)0.8550.6 (0.5, 0.7)0.97 (0.81, 1.17)0.7690.8 (0.7, 0.8)0.85 (0.75, 0.95)0.0092.8 (2.4, 3.2)0.91 (0.74, 1.11)0.3502.9 (2.6, 3.2)0.86 (0.76, 0.99)0.037Ethnic origin Achuar91 (39.6)195 (32.8)17.7 (14.5, 21.7)Ref—9.3 (8.3, 10.3)Ref—0.8 (0.7, 0.9)Ref—0.8 (0.8, 0.9)Ref—2.5 (2.2, 2.8)Ref—2.2 (2.0, 2.4)Ref— Quechua and Kichwa79 (34.3)231 (38.9)20.1 (16.1, 25.2)1.19 (0.83, 1.72)—9.9 (8.8, 11.1)1.14 (0.95, 1.38)—0.6 (0.5, 0.6)0.77 (0.62, 0.96)—0.8 (0.7, 0.9)0.93 (0.80, 1.09)—3.6 (3.0, 4.4)1.48 (1.17, 1.89)—3.3 (3.0, 3.7)1.54 (1.30, 1.81)— Mestizo, Kukama, and other peoples60 (26.1)168 (28.3)14.6 (11.8, 18.1)0.88 (0.60, 1.30)0.25113.2 (11.6, 15.0)1.48 (1.22, 1.78)less than 0.001<0.0010.5 (0.4, 0.6)0.62 (0.50, 0.79)0.0010.9 (0.8, 1.0)0.91 (0.77, 1.07)bless than 0.001<0.0013.1 (2.6, 3.7)1.37 (1.07, 1.75)0.0063.9 (3.4, 4.5)1.76 (1.44, 2.16)less than 0.001<0.001River basin Marañón55 (23.9)145 (24.4)14.3 (11.4, 17.9)Ref—12.7 (11.0, 14.6)Ref—0.5 (0.4, 0.6)Ref—0.9 (0.8, 1.0)Ref—3.2 (2.6, 4.0)Ref—4.2 (3.6, 4.9)Ref— Pastaza68 (29.6)198 (33.3)24.2 (18.7, 31.4)1.88 (1.24, 2.85)—10.2 (9.0, 11.6)0.83 (0.68, 1.02)—0.5 (0.4, 0.6)1.19 (0.95, 1.51)—0.6 (0.6, 0.7)0.86 (0.74, 1.01)—3.5 (2.9, 4.2)1.03 (0.76, 1.39)—3.0 (2.7, 3.3)0.72 (0.58, 0.91)— Tigre15 (6.5)51 (8.6)13.0 (8.6, 19.7)0.87 (0.56, 1.33)—8.5 (6.6, 11.0)0.68 (0.50, 0.94)—0.7 (0.6, 0.9)1.55 (1.15, 2.09)—1.5 (1.2, 1.8)1.91 (1.52, 2.39)—4.0 (2.3, 7.0)1.18 (0.74, 1.88)—3.9 (3.1, 5.0)0.99 (0.66, 1.49)— Corrientes92 (40.0)200 (33.7)16.6 (13.8, 19.9)1.11 (0.79, 1.56)0.01210.0 (9.0, 11.0)0.78 (0.64, 0.94)0.0560.7 (0.6, 0.8)1.60 (1.26, 2.03)0.0030.9 (0.8, 1.0)1.22 (1.03, 1.45)bless than 0.001<0.0012.5 (2.1, 2.8)0.72 (0.55, 0.95)0.0182.2 (2.0, 2.4)0.54 (0.43, 0.68)less than 0.001<0.001 Total fish consumption (times 100 grams×100g)c1.3 plus or minus 1.31.3±1.31.6 plus or minus 1.51.6±1.5—1.00 (0.99, 1.02)0.426—1.00 (0.99, 1.01)0.9541.00 (0.98, 1.01)0.404—1.00 (1.00, 1.01)0.594—0.99 (0.98, 1.00)0.1081.01 (1.00, 1.01)0.038Fish offal consumption No82 (35.7)150 (25.3)21.1 (17.2, 26.0)Ref—11.9 (10.4, 13.6)Ref—0.6 (0.6, 0.7)Ref—0.8 (0.7, 0.9)Ref—2.8 (2.4, 3.3)Ref—3.0 (2.6, 3.4)Ref— Yes148 (64.3)444 (74.7)15.9 (13.7, 18.6)0.80 (0.60, 1.08)0.15010.1 (9.3, 10.9)0.85 (0.71, 1.01)0.0720.6 (0.5, 0.6)0.92 (0.76, 1.11)0.3810.9 (0.8, 0.9)1.03 (0.90, 1.18)0.6853.1 (2.7, 3.5)1.06 (0.86, 1.32)0.5783.0 (2.8, 3.3)0.94 (0.79, 1.13)0.524Alcohol consumption (only greater than or equal to 12≥12 y old) No—495 (83.3)———10.8 (10.1, 11.7)Ref————0.8 (0.8, 0.9)Ref————3.0 (2.8, 3.3)Ref— Yes—99 (16.7)———9.1 (7.8, 10.5)0.86 (0.70, 1.06)0.161———0.9 (0.8, 1.0)1.17 (0.99, 1.38)0.070———3.0 (2.5, 3.6)1.07 (0.86, 1.34)0.550Smoking (only greater than or equal to 12≥12 y old) No—531 (89.4)———10.7 (9.9, 11.5)1.00 (1.00, 1.00)————0.8 (0.8, 0.9)1.00 (1.00, 1.00)————3.0 (2.8, 3.2)1.00 (1.00, 1.00)— Yes—63 (10.6)———9.2 (7.6, 11.1)0.88 (0.73, 1.07)0.219———1.0 (0.8, 1.2)1.28 (0.98, 1.65)0.073———3.0 (2.3, 3.9)1.03 (0.78, 1.36)0.840Burning of household waste No128 (55.7)330 (55.6)15.9 (13.6, 18.7)Ref—10.8 (9.8, 11.8)Ref—0.6 (0.5, 0.7)Ref—0.9 (0.8, 0.9)Ref—2.9 (2.6, 3.3)Ref—3.0 (2.8, 3.3)Ref— Yes102 (44.3)264 (44.4)20.0 (16.5, 24.2)1.26 (0.92, 1.74)0.16210.2 (9.2, 11.3)1.00 (0.85, 1.18)0.9910.6 (0.5, 0.7)1.02 (0.85, 1.23)0.8260.8 (0.7, 0.9)0.87 (0.76, 1.00)b0.0543.1 (2.7, 3.6)1.07 (0.85, 1.35)0.5603.0 (2.7, 3.4)0.99 (0.83, 1.18)0.934Main source of water for consumption Public water source116 (50.4)265 (44.6)15.4 (12.9, 18.4)Ref—9.6 (8.7, 10.6)Ref—0.6 (0.5, 0.7)Ref—0.8 (0.7, 0.9)Ref—3.2 (2.8, 3.7)Ref—3.1 (2.8, 3.4)Ref— Well or spring water56 (24.3)170 (28.6)27.6 (21.8, 34.8)1.69 (1.16, 2.46)—11.1 (9.9, 12.6)1.13 (0.94, 1.37)—0.6 (0.5, 0.8)1.12 (0.89, 1.42)—0.8 (0.7, 0.9)1.04 (0.90, 1.20)—2.4 (2.0, 2.9)0.76 (0.59, 0.99)—2.4 (2.1, 2.6)0.78 (0.65, 0.94)— Rain22 (9.6)68 (11.4)15.4 (10.7, 22.3)0.99 (0.64, 1.53)—12.3 (9.8, 15.4)1.29 (0.98, 1.70)—0.6 (0.4, 0.7)1.00 (0.75, 1.33)—1.2 (1.0, 1.4)1.49 (1.21, 1.82)—3.0 (2.1, 4.4)0.97 (0.65, 1.45)—4.5 (3.6, 5.6)1.41 (1.07, 1.86)— Surface water (river, ravine, lagoon)36 (15.7)91 (15.3)14.6 (10.9, 19.7)0.81 (0.53, 1.24)0.01111.0 (9.2, 13.1)1.10 (0.90, 1.34)0.3130.7 (0.6, 0.8)1.19 (0.91, 1.55)0.5680.8 (0.7, 1.0)1.15 (0.93, 1.41)0.0063.2 (2.6, 4.1)0.98 (0.71, 1.35)0.2623.2 (2.7, 3.9)1.10 (0.84, 1.43)0.001Main bathing place Well38 (16.5)118 (19.9)25.9 (18.6, 36.1)Ref—10.4 (9.0, 12.0)Ref—0.6 (0.4, 0.7)Ref—0.8 (0.7, 0.9)Ref—2.8 (2.2, 3.5)Ref—2.6 (2.2, 2.9)Ref— Surface water (river, ravine, lagoon)156 (67.8)399 (67.2)16.5 (14.2, 19.1)0.68 (0.47, 0.98)—10.5 (9.7, 11.4)1.03 (0.85, 1.24)—0.6 (0.5, 0.7)1.04 (0.79, 1.35)—0.8 (0.8, 0.9)1.07 (0.91, 1.26)—3.2 (2.9, 3.6)1.09 (0.85, 1.41)—3.4 (3.1, 3.7)1.32 (1.10, 1.58)— Others36 (15.7)77 (13.0)15.7 (11.9, 20.6)0.82 (0.66, 1.02)0.07110.6 (8.8, 12.8)0.98 (0.77, 1.26)0.9060.6 (0.5, 0.8)0.82 (0.66, 1.02)0.7450.8 (0.7, 0.9)0.94 (0.77, 1.16)0.3262.3 (1.7, 3.1)0.82 (0.66, 1.02)0.1752.1 (1.7, 2.5)0.80 (0.60, 1.08)0.001Residence at less than 1<1 h walking None of these places75 (32.6)160 (26.9)16.8 (13.6, 20.7)Ref—10.1 (8.9, 11.6)Ref—0.6 (0.5, 0.7)Ref—0.8 (0.7, 0.9)Ref—3.1 (2.7, 3.6)Ref—3.3 (2.9, 3.8)Ref— Active oil infrastructures30 (13.0)117 (19.7)24.2 (16.4, 35.7)1.38 (0.84, 2.25)—11.7 (10.0, 13.6)1.16 (0.91, 1.48)—0.5 (0.4, 0.7)0.84 (0.63, 1.12)—0.8 (0.7, 0.9)1.10 (0.91, 1.33)—2.3 (1.8, 2.9)0.70 (0.51, 0.95)—2.8 (2.5, 3.3)0.96 (0.75, 1.22)— Oil spill, environmental remediation spot107 (46.5)288 (48.5)17.1 (14.3, 20.4)0.97 (0.66, 1.44)—10.5 (9.5, 11.6)1.05 (0.86, 1.30)—0.6 (0.5, 0.7)1.02 (0.80, 1.29)—0.9 (0.8, 1.0)1.25 (1.05, 1.49)—3.4 (2.9, 4.0)1.07 (0.84, 1.38)—3.0 (2.7, 3.3)0.96 (0.77, 1.19)— Old infrastructures (not in use)18 (7.8)29 (4.9)15.4 (9.7, 24.6)0.85 (0.50, 1.44)0.3808.7 (6.8, 11.2)0.89 (0.62, 1.29)0.4810.7 (0.5, 0.9)1.08 (0.77, 1.50)0.4230.8 (0.6, 1.0)1.02 (0.80, 1.31)0.0932.0 (1.4, 2.7)0.60 (0.43, 0.84)b0.0042.8 (2.1, 3.7)0.88 (0.58, 1.33)0.942Vegetable garden at less than 1<1 h walking None of these places102 (44.3)261 (43.9)16.6 (13.7, 20.1)Ref—10.8 (9.8, 12.0)Ref—0.6 (0.5, 0.7)Ref—0.8 (0.7, 0.9)Ref—3.0 (2.6, 3.4)Ref—3.3 (3.0, 3.7)Ref— Active oil infrastructures31 (13.5)87 (14.6)19.8 (13.3, 29.6)1.05 (0.64, 1.74)—11.1 (9.4, 13.0)0.99 (0.79, 1.25)—0.6 (0.5, 0.8)1.04 (0.77, 1.41)—0.8 (0.7, 0.9)0.96 (0.79, 1.15)—2.1 (1.7, 2.6)0.69 (0.52, 0.93)—2.6 (2.2, 2.9)0.79 (0.64, 0.98)— Oil spill, environmental remediation spot93 (40.4)232 (39.1)18.2 (15.2, 21.8)1.09 (0.76, 1.55)—10.2 (9.1, 11.4)0.90 (0.75, 1.08)—0.6 (0.5, 0.7)1.02 (0.83, 1.26)—0.9 (0.8, 1.0)1.20 (1.03, 1.39)—3.5 (2.9, 4.2)1.14 (0.89, 1.46)—2.9 (2.6, 3.3)0.88 (0.72, 1.08)— Old infrastructures (not in use)4 (1.7)14 (2.4)14.4 (3.2, 64.5)0.98 (0.45, 2.12)0.9737.8 (5.8, 10.6)0.73 (0.55, 0.96)0.1740.6 (0.2, 2.0)1.08 (0.47, 2.48)0.9910.5 (0.4, 0.7)0.75 (0.54, 1.04)b0.0311.9 (0.8, 4.7)0.61 (0.41, 0.90)0.0052.6 (1.9, 3.6)0.85 (0.55, 1.32)0.246Use of crude oil to keep insects away from the house No138 (60.0)368 (62.0)16.3 (13.8, 19.4)Ref—9.9 (9.1, 10.8)Ref—0.6 (0.5, 0.7)Ref—0.8 (0.8, 0.9)Ref—3.3 (2.9, 3.7)Ref3.2 (2.9, 3.5)Ref— Yes92 (40.0)226 (38.0)19.7 (16.6, 23.4)1.14 (0.85, 1.53)0.39911.5 (10.3, 12.9)1.12 (0.95, 1.32)0.2020.6 (0.5, 0.7)1.00 (0.83, 1.22)0.9690.8 (0.7, 0.9)0.96 (0.84, 1.10)0.5692.6 (2.3, 3.1)0.83 (0.66, 1.05)0.1242.8 (2.5, 3.1)0.91 (0.75, 1.09)0.305Contact with crude oil in the last 6 months (only greater than or equal to 12≥12 y old) No—513 (86.4)———10.6 (9.9, 11.5)Ref————0.8 (0.8, 0.9)Ref————3.1 (2.8, 3.3)Ref— Yes—81 (13.6)———9.8 (8.3, 11.5)0.89 (0.72, 1.10)0.301———0.8 (0.7, 0.9)1.02 (0.85, 1.23)0.848———2.8 (2.3, 3.4)0.95 (0.75, 1.20)0.645Participation in environmental remediation activities in the last 6 months (only greater than or equal to 12≥12 y old)d No—449 (75.6)———10.7 (9.9, 11.5)Ref————0.8 (0.8, 0.9)Ref————3.1 (2.9, 3.4)Ref— Yes—145 (24.4)———10.0 (8.8, 11.4)0.95 (0.80, 1.12)0.532———0.9 (0.8, 1.0)1.11 (0.95, 1.29)0.185———2.7 (2.4, 3.1)0.92 (0.75, 1.12)0.388Euclidean distance to closest oil processing facility (times 10 kilometers×10km)2.5 plus or minus 3.92.5±3.92.2 plus or minus 3.52.2±3.5—0.96 (0.92, 1.00)0.067—1.00 (0.98, 1.03)0.747—0.97 (0.95, 0.99)0.006—0.99 (0.97, 1.01)0.185—1.05 (1.02, 1.08)0.002—1.06 (1.04, 1.09)less than 0.001<0.001Minimum upstream fluvial distance processing facility (times 10 kilometers×10km)e14.9 plus or minus 19.214.9±19.215.8 plus or minus 20.315.8±20.3—0.99 (0.98, 1.00)0.053—1.00 (1.00, 1.01)0.218—0.99 (0.99, 1.00)0.00—1.00 (0.99, 1.00)0.034—1.00 (1.00, 1.01)0.108—1.01 (1.00, 1.02)less than 0.001<0.001Note: Individual linear regression models adjusted for age and sex, unless otherwise noted. p-Values based on Wald test less than 0.05<0.05. Limit of detection was 2.5 micrograms per liter2.5μg/L for U-As and U-Hg and 0.5 microgram per liter0.5μg/L for U-Cd. —, Not applicable; CI, confidence interval; GM, geometric mean; GMR, geometric mean ratio; Ref, reference.aIndividual model adjusted for sex.bIndividual model adjusted for age.cRestricted to total fish consumption less than or equal to 7 kilograms per week≤7kg/wk (166 participants less than 12<12 y old; 433 participants greater than or equal to 12≥12 y old).dEnvironmental remediation activities include handling of solid waste, cleaning of environmental liabilities or contaminated sites, and reforestation of contaminated areas.eOnly among those living downstream from central production facilities (161 participants less than 12<12 y old; 410 participants greater than or equal to 12≥12 y old).U-Hg concentration (Table 1) increased with age among adults and were higher in the Kukama, mestizo (i.e., peoples that do not identify as belonging to an indigenous group themselves, often mixed-blood people) and other peoples, and among those living around the Marañón basin. Elevated U-Hg was also associated with increased fish consumption, which was higher in the Marañón (1,842 grams per week1,842g/wk) than in other river basins. Elevated mercury in Amazonian fish has been associated with oil contamination,5 and there is evidence that consumption of freshwater fish is associated with U-Hg concentrations.6 However, previous studies from the same region, suggest that the main route of exposure to mercury in the area is through dermal uptake of mercury present in the water.7 This is consistent with our results given that concentrations of U-Hg were 1.09 and 1.32 times higher among children and adults bathing in river water compared with those bathing in wells, and 1.42 times higher among adults consuming rain water compared with those drinking from a public water source.U-As concentrations (Table 1) decreased slightly with age in adults, tended to be higher among children who drank well water and, similar to U-Hg, were highest among Kukama, mestizo and other peoples, and among those living around Marañón. Elevated arsenic of geologic origin has been reported in the aquifers of the western Amazon8 and at relatively high concentrations in crude oil9; however, the source of arsenic in the study area remains unknown.U-Cd concentrations (Table 1) increased with age in adults and were higher in females. The highest concentrations were observed for the Achuar People and among those living around the Corrientes and Tigre river basins. Historically, these two basins have had relatively greater oil extraction activity and higher volumes of produced water released than the Pastaza and Marañón basins (discussed by O’Callaghan-Gordo et al.3) Additional factors associated with elevated U-Cd included proximity of residences or vegetable gardens to oil spill sites and participation in oil spill remediation activities. Consumption of contaminated vegetables is a known route of exposure to cadmium, and high levels of cadmium in vegetables are associated with environmental conditions.10Multivariable analyses did not indicate substantially different patterns from the univariable analyses (supporting information). Concentrations without creatinine correction were available for another 211 study participants. Models including noncorrected concentration of metals (lowercase italic n equals 1,035n=1,035) yielded similar results (supporting information).A considerable proportion of the population of children and adults exceeded the recommended RV levels. Concentrations of the three metals were associated with the sources of water for consumption and U-Hg was also associated with the sources of water for bathing. Remarkably, mercury can be absorbed through dermal uptake.7 Participation in oil activities was associated with U-Cd, and the higher levels were observed in Corrientes and Tigre river basins, which are considered the two most polluted river basins.The strengths of this research are the large sample size, the random sampling of families from different river basins with varying characteristics, and the active participation of the indigenous organizations in this research. Without the cooperation of the indigenous organizations it would not have been possible to conduct such a study in a remote area of the Amazon.The observed pattern of high concentrations for all metals supports anthropogenic sources of contamination, including oil extraction activities. The identification of high concentrations of metals in a population living in a nonindustrial setting is concerning regarding health effects, such as childhood neurodevelopment and chronic diseases, through long-term exposure. Prevention of these exposures and provision of clean water and ensuring food security are a high priority for the indigenous populations living in these river basins.AcknowledgmentsThis study was funded by National Institute of Health of Peru. We acknowledge support from the Spanish Ministry of Science and Innovation through the Centro de Excelencia Severo Ochoa 2019–2023 Program (CEX2018-000806-S). Supporting information can be found at the website of the project: https://www.isglobal.org/-/levels-of-and-risk-factors-for-exposure-to-heavy-metals-and-hydrocarbons-in-the-inhabitants-of-the-communities-of-the-pastaza-tigre-corrientes-and-mar.References1. Epstein PR, Selber J. 2002. Oil: A Life Cycle Analysis of Its Health and Environmental Impacts. http://oneplanetfellows.pbworks.com/w/file/fetch/11680650/Oil_Impacts_full report.pdf [accessed 23 February 2023]. Google Scholar2. Ormaeche Macassi M, Llamocca Rodríguez A, Barclay Rey de Castro F, Okamoto Mendoza T. 2020. 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Crossref, Medline, Google ScholarThe authors declare no conflicting interests.FiguresReferencesRelatedDetails Vol. 131, No. 5 May 2023Metrics About Article Metrics Publication History Manuscript received29 July 2022Manuscript revised27 February 2023Manuscript accepted29 March 2023Originally published3 May 2023 Financial disclosuresPDF download License information EHP is an open-access journal published with support from the National Institute of Environmental Health Sciences, National Institutes of Health. All content is public domain unless otherwise noted. Note to readers with disabilities EHP strives to ensure that all journal content is accessible to all readers. However, some figures and Supplemental Material published in EHP articles may not conform to 508 standards due to the complexity of the information being presented. If you need assistance accessing journal content, please contact [email protected]. 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