Dairy ruminant exposure to persistent organic pollutants and excretion to milk

Abstract

Human activities produce polluting compounds such as persistent organic pollutants (POPs), which may interact with agriculture. These molecules have raised concern about the risk of transfer through the food chain via the animal product. POPs are characterised by a strong persistence in the environment, a high volatility and a lipophilicity, which lead to their accumulation in fat tissues. These compounds are listed in international conventions to organise the information about their potential toxicity for humans and the environment. The aim of this paper is to synthesise current information on dairy ruminant exposure to POPs and the risk of their transfer to milk. Three major groups of POPs have been considered: the polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), the polychlorobiphenyls (PCBs) and the polycyclic aromatic hydrocarbons (PAHs). The results show that contamination of fodder and soil by these compounds is observed when they are exposed to emission sources (steelworks, cementworks, waste incinerators or motorways) compared with remote areas. In general, soil contamination is considered higher than plant contamination. Highest concentrations of POPs in soil may be close to 1000 ng/kg dry matter (DM) for PCDD/Fs, to 10 000 mg/kg DM for PAHs and 100 μg/kg DM for PCBs. The contamination of milk by POPs depends on environmental factors, factors related to the rearing system (fodder and potentially contaminated soil, stage of lactation, medical state of the herd) and of the characteristics of the contaminants. Transfer rates to milk have been established: for PCBs the rate of transfer varies from 5% to 90%, for PCDD/Fs from 1% to 40% and for PAHs from 0.5% to 8%. The differential transfer of the compounds towards milk is related to the hydrophobicity of the pollutants as well as to the metabolic susceptibility of the compounds.

PAHs concentration in heat-treated milk samples

“…Because the lactating cows are likely to intake varying quantities of contaminants from soil during grazing (Rychen, Jurjanz, Toussaint, & Feidt, 2008), PAHs can be transferred through the organism and excreted to milk due to their ability to cross blood mammary barrier . The quantity of PAHs secreted in milk would constitute a risk to human consumers (Luitz et al, 2006), especially for children (Ciecierska & Obiedzinski, 2010).…”

Polybrominated Diphenyl Ether Contamination in Soil, Vegetation, and Cow Milk From a High-Mountain Pasture in the Italian Alps

“…Analyzing the PBDE congener ratio between milk and vegetation, great differences in fingerprint were found (Fig. 1), even if the accumulation of pollutants in milk mainly occurs by way of vegetation (Rychen et al 2008). Moreover, the milk fingerprint was also different from the soil one, although cows can ingest from 1 to 10% of their diet as soil, thus contributing to POP uptake (Mamontova et al 2007).…”

Presença de hidrocarbonetos policíclicos aromáticos em produtos alimentícios e a sua relação com o método de cocção e a natureza do alimento

“…Desta forma, o leite pode ser visto como um indicador indireto para poluição ambiental, tendo como referência seu local de obtenção (NACCARI et al, 2006). Certas propriedades de alguns HPA, como menor massa molecular e maior volatilidade, facilitam seu transporte e depósito sobre as pastagens, as quais, posteriormente, serão consumidas por vacas em lactação (GROVA et al, 2002;RYCHEN et al, 2005RYCHEN et al, , 2008. Os HPA ingeridos podem ser transferidos para o leite, devido à sua capacidade de atravessar a barreira entre o sangue e a glândula mamária (GROVA et al, 2002).…”