Research Article Paraquat in Surface Water of Some Streams in Mai Chau Province, the Northern Vietnam: Concentrations, Profiles, and Human Risk Assessments Nguyen Thi Hue , 1,2 Thi Phuong Mai Nguyen, 1 Hoang Nam, 1 and Nguyen Hoang Tung 1 1 Institute of Environmental Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam 2 Hanoi University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam Correspondence should be addressed to Nguyen Ti Hue; nthue2003@ietvn.vn Received 16 August 2017; Revised 25 December 2017; Accepted 31 December 2017; Published 25 February 2018 Academic Editor: Jaime Villaverde Copyright © 2018 Nguyen Ti Hue et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te concentrations and profles of paraquat, a kind of herbicide, were studied in water samples taken from a stream fowing through fve villages of Mai Chau province, the Northern Vietnam, during dry and rainy seasons. In this study, paraquat was found at almost the sampling sites and showed an average concentration for paraquat to be 30.69 g/L and with a maximum of 134.08 g/L. Te herbicide concentration tended to be the highest on the dry season because of the least rainfall and also the highest evaporation rate of water in the stream. For risk assessment of human health, a hazard index (HI) value was calculated for estimating the risk towards the residents. HQ in the dry and rainy season is from 0.0001 to 0.2448 and from 0.0001 to 0.0279, respectively. Te results showed a minimum risk; however, there are concerns toward the danger of long-term exposure to the residents from the stream that could afect their life quality. 1. Introduction Paraquat (1,1  -dimethyl-4,4  -bipyridylium dichloride), a kind of a nonselective, contact, broad-spectrum herbicide, has been widely used as a herbicide for many decades [1–3]. Te herbicide is sold in about 130 countries for use on large and small farms, paddies, and nonagricultural weed control. Gramoxone is the commercial name for paraquat. Te use of paraquat has been discussed for decades in international, national, and nongovernmental organizations [4–16]. Te herbicide under aerobic conditions is rapidly reox- idized by accepting an electron from nicotine adenine din- ucleotide phosphate (NADPH) with resulting formation of the superoxide or other oxygen radicals. Both the superoxide and the radicals damage cell membranes and cytoplasm from NADPH depletion, free radical generation, and lipid peroxidation, or some combination of these factors [17–19]. It is poorly absorbed through intact skin, but penetration is considerably increased by damage to the skin, which is of par- ticular concern because paraquat itself is a skin irritant [20]. With damage mentioned above, using paraquat may pose potential environmental hazards to humans or surrounding ecosystems [21, 22]. Its acute toxicity at oral LD50 ranges from 4 to 40mg kg −1 [23]. However, up to 3.5 mg kg −1 can be absorbed through the skin or respiratory route without acute toxic damage. Besides irreversible human lung damage [24], recent concern has been raised about an association of Parkinson’s disease to paraquat or a combination of paraquat and fungicide exposures [25]. Tere have been few studies on their appearance, persistence, and distribution in the environment [17, 26], and none has been performed in the Southeastern Asia area. However, the results that have been obtained are alarming. In water environment, paraquat is adsorbed onto particles and sediment with a half-life time to be between 2 and 820 years depending on sunlight and depth of water, and it has been found in both surface waters and groundwater [27]. Paraquat is not easily degraded chemically or microbiologically and demonstrates long-term persistence in river waters with more than 80% remaining afer 56 days of incubation [28]. In water, this compound is completely Hindawi Journal of Chemistry Volume 2018, Article ID 8521012, 8 pages https://doi.org/10.1155/2018/8521012