Environmental sample collection and analysis

Several types of environmental samples were collected. In both countries, surface wipe and area air samples were collected. In Thailand, samples of rice, soil, surface water, personal, and environmental air samples were collected in addition. Details on the methods used to collect and analyze each sample type are below.

2.2.3.1 Rice and soil

Locally-grown rice samples were purchased from various parts of the research site in Thailand. A one-kg sample of rice was weighed and collected in Ziploc bags. No rice or other agricultural samples were collected from Chile as the study sites were primarily urban areas.

Soil samples were collected from various parts of the community, including in yards of homes and in communal areas using EPA soil collection procedures [65]. One-kg samples were mixed using quartering method, debris removed, and stored in a Ziploc bag.

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Rice and soil samples were stored in a cool, dry location prior to analysis. Samples were analyzed for concentration of 8 heavy metals associated with electronic waste recycling: Cd, Cu, Fe, Mn, Ni, Pb, and Zn. These metals were selected based on their prevalence in electronic products [66], [67]. The International Organization for Standardization (ISO)-certified Thailand Central Laboratory used microwave-assisted acid digestion followed by Atomic Absorption Spectrophotometry to analyze rice and soil samples [68].

For comparison purposes, three recommended reference levels were used to evaluate metal concentrations in rice, as no one reference type was available for all seven metals. The Maximum Level (ML) is set by the Joint Food and Agriculture Organization of the United Nations/World Health Organization (Joint FAO/WHO) as the maximum concentration of a substance permitted in a commodity for human consumption [69]-[71]. The Provisional Maximum Tolerable Daily Intake (PMTDI) is also set by the Joint FAO/WHO, and is the maximum amount of a contaminant that can be ingested per day by body weight; this recommendation accounts for toxicants that accumulate within the body [72], [73]. The Tolerable Upper Intake Limit (TUIL), set by the Food and Nutrition Board at the Institute of Medicine, National Academies of the United States, is the maximum daily amount of a chemical that can be ingested where no health effects are expected for most individuals [74]. Rice sample concentrations from Thailand were calculated to be comparable to the associated reference type. For TUIL and PMTDI, the dietary intake was calculated for rice samples using a 60 kg body weight and 0.28 kg rice consumed daily, based on values taken from a study on a northeastern Thailand population [75].

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2.2.3.2 Surface water

Water samples were collected from two areas: 1 and > 1 km of the community refuse dump. Samples were collected according to EPA surface water sampling protocol SESDPROC- 201-R3 [76]. Samples were collected in high-density polyethylene bottles and stored at 4°C prior to analysis. Water samples were analyzed at the Thailand Central Laboratory using ICP-MS [77]. Samples were tested for Cd, Cu, and Pb as these elements are found in electronics, are known to impact human health (Cu toxicity occurs at levels beyond those needed for biological

functioning), and because of the existence of regulatory limits for Cu and Pb in drinking water to which our results could be compared [66], [67], [78].

2.2.3.3 Wipe and air samples

Wipe samples were collected in Thailand and in Chile using OSHA surface wipe sampling protocols [79]. A 10 cm x 10 cm template was used to collect surface dust from areas where food was prepared or consumed, as well as on work benches. Samples were stored in 100- mL plastic centrifuge tubes and sealed with parafilm for storage.

Three types of air samples were collected. Area samples were collected in Thailand and Chile by mounting the pump and cassette on or adjacent to the subject’s work station.

Environmental samples were collected in Thailand by affixing the pump and cassette to a tripod and placing the tripod in a communal area, such as a community temple. Environmental air samples were not collected during rain events. Finally, personal breathing zones (PBZ) samples were collected in Thailand by attaching the pump to the subject and placing the filter cassette in the sampled individual’s breathing zone.

All air samples were collected using SKC Airchek-52 Personal Air Sampling Pumps. Pumps were calibrated before and after sampling events using a DryCal to check flow rate. The

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average of the pre- and post-sampling flow rates was used to later calculate the volume of air sampled. Samples were collected on 37-mm cassette filters with 0.8 μm cellulose ester

membranes. The target air sampling time was 8-10 hours, or one work shift; however, subject activities, such as short working hours, occasionally limited sampling time. After collection, cassettes were sealed with parafilm and stored into a Ziplock bag.

Wipe and air samples were stored in cool, dry conditions until analysis at Bureau Veritas Laboratory in Novi, Michigan using OSHA method 125G for Inductively Coupled Plasma (ICP) analysis [80]. Wipe and air samples were analyzed for 13 metals associated with e-waste

recycling: antimony (Sb), Beryllium (Be), Cd, chromium (Cr), cobalt (Co), Cu, Fe, Pb, Mn, molybdenum (Mo), Ni, vanadium (V), and Zn. These metals were selected because they are known to be included in electronic products, and thus might be present in air and wipe samples of e-waste recycling areas [67], [81]. One field blank was collected and analyzed for each day of sampling for both wipe and air samples. All samples were blank-corrected.