Impact of environmental variables on PCDD/F and dl-PCB levels in dairy milk of the farming region of Chile

Cien. Inv. Agr. 45(2):109-119. 2018 www.rcia.uc.cl animal production DOI 10.7764/rcia.v45i2.1887 research paper Impact of environmental variables on PCDD/F and dl-PCB levels in dairy milk of the farming region of Chile Nicolás Pizarro-Aránguiz1, Diego García-Mendoza2, Rubén Muñoz3, Betty San Martín3, and Rodrigo Morales1 Instituto de Investigaciones Agropecuarias, INIA Remehue. Ruta 5 Norte km 8. P.O.Box 24-0, Osorno, Chile. 2 Wageningen University, Division of Toxicology. 6708 PB Wageningen, Netherlands 3 Universidad de Chile, Faculty of Veterinary Science, Laboratory of Veterinary Pharmacology. Av. Sta. Rosa 11735, 8820808 Santiago, Chile 1 Abstract N. Pizarro-Aránguiz, D. García-Mendoza, R. Muñoz, B. San Martín, and R. Morales. Impact of environmental variables on PCDD/F and dl-PCB levels in dairy milk of the farming region of Chile. 2018. Cien. Inv. Agr. 45(2): 109-119. According to a One Health perspective, the importance of persistent organic pollutants (POPs) must be assessed because of their impact on the environment, food chain and human health. However, information on these toxic compounds is limited in Latin America and the Caribbean region. Chile is no exception; therefore, this work aimed to explain previously reported dioxin levels in cow-milk samples by utilizing regression with meteorological/geographical data that were collected over a three-year survey. To accomplish this aim, a stepwise general multiple regression analysis was carried out for polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (dl-PCBs). The best statistical adjustments were achieved only for highly present congeners. Regarding PCDD/F congeners, the most relevant and significant (P <0.05) factors were the year (mostly a negative coefficient), the season, and the hectares affected by forest fires. In the case of dl-PCB congeners, there was a clear, positive relationship with the geographic parameter (UTM), and this result was consistent with previous findings that dl-PCB congeners show a trend with latitude. In contrast, wind speed was a significant negative coefficient for dl-PCBs. Despite existing knowledge on pollutant levels in milk, this study is relevant to better understand these findings in the Latin America and Caribbean regions. Keywords: Dioxin-like polychlorinated biphenyls, environmental variables, food contamination, persistent organic pollutants, polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans. Introduction Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and Received Oct 26, 2017. Accepted Jun 27, 2018. Corresponding author: dioxin-like polychlorinated biphenyls (dl-PCBs) are considered to be persistent organic pollutants (POPs) due to long-range atmospheric transport, environmental persistence, and a capacity for bioaccumulation in animal fat tissue (Abad et al., 2002). PCDD/Fs are chemical by-products of several industrial and combustion processes. While 110 CIENCIA E INVESTIGACIÓN AGRARIA large quantities of dl-PCBs were produced over the last century for industrial uses, production of these chemicals have been recently banned. These pollutants are toxic even in small concentrations and are considered carcinogenic compounds (Erickson et al., 2011). Public programs for measuring environmental pollutants, as established under the Stockholm Convention, are particularly concerned about food safety, since consumption of contaminated food is the major pathway of exposure for humans. These programs aim to prevent high pollutant levels in animal feed and animal origin products for human consumption (Kotz, 2014). Many previous studies have assessed dioxin and dioxin-like compound levels in animal products for human consumption, feed, and feed additives (Esposito et al., 2009, Pizarro-Aranguiz et al., 2015, Pemberthy et al., 2016, San Martín et al., 2016) could be differential pollutant levels among animal products, including cow milk and dairy products, that are related to human exposure and represent a considerable proportion of total dietary exposure. For instance, dairy and beef cattle researchers have shown that POPs initially enter the food chain by atmospheric deposition from local emission sources that reach soils and pasture, which are in turn consumed by livestock (Rychen et al., 2008). The other alternative is by ingestion of contaminated feed supplements (i.e., risk source) and the production cycle (Lake et al., 2013, Shunthirasingham et al., 2013). Bioaccumulation in animal tissue from feed sources depends on the congener patterns and matrix of PCDD/Fs and dl-PCBs; in fact, there is a wide range of transfer factors for each congener (Kotz, 2014). Additionally, environmental conditions at animal farms, such as meteorological and geographical factors, can cause variations in atmospheric deposition and thus bioaccumulation in milk (Schulz et al., 2005, Shunthirasingham et al., 2013). It is well known that PCDD/Fs and dl-PCBs are present in the atmosphere in the form of gas and particles, and the partition process is governed by the equilibrium between these two phases, which depends on the various environmental factors that affect the final deposition, such as air temperature or vapor pressure (Aristizábal et al., 2011, Shunthirasingham et al., 2013). Furthermore, a correlation has been recognized between air quality and meteorological variables, which directly affects the accumulation and diffusion of pollution (Halfon et al., 2009). Animal farming in Chile occurs between the latitudes of 32 and 41°S, in the central valley, ranging from the metropolitan to the Los Lagos regions, which includes the most populated cities in the country. These regions have an increasing latitudinal trend in precipitation, a decreasing trend in mean temperature and have the following seasons: summer (December to February), autumn (March to May), winter (June to August), and spring (September to November). Bovine production (dairy and beef cattle) is concentrated in this area, and at least 70% of the total production is concentrated in the southern area of the valley. The main production system used in this area corresponds to a free-range system based on pasture and strategic use of supplementary feeds during the winter and summer seasons, such as forage and concentrates. Confined production systems, which use conserved forage and concentrates (grains, agricultural subproducts, etc.), are typical in the northern area of the valley (i.e., Metropolitan and Valparaiso regions) because of the lack of space for extensive pasture areas. Furthermore, there are other conditions of the central valley that should be investigated and warrant environmental pollution studies and include the following: (1) anthropogenic factors such as population size, particularly as more than half of Chile’s population lives within the central valley, which leads to massive emissi (...truncated)