Lead and cadmium levels in raw bovine milk and dietary risk assessment in areas near petroleum extraction industries

Abstract

Oil fields are a source of heavy metal pollution, but few studies have evaluated its impact on the intake of these contaminants through milk, an important food especially for children. From February 2015 to 2016, 118 samples of raw cow's milk, 14 of fodder and 8 of water in Southwest Iran were collected from farms close to oil fields or related industries. Lead (Pb) and cadmium (Cd) levels were evaluated by graphite furnace atomic absorption spectrometry. Mean±SE in milk and fodder were 47.0±3.9 and 54.0±6.9μg/kg for Pb, and 4.7±1.0 and 3.5±1.3μg/kg for Cd. No Pb or Cd was detected in water. Most milk samples (82.2%) for Pb were above the permissible limits (20μg/kg). Exposure to Pb and Cd from milk consumption was calculated in two scenarios: mean and maximum exposure for the age range of 2-90years. The intake of an average Iranian adult (25years, 60kg b. w., 0.14kg milk/day) would be 6.6μg Pb and 0.66μg Cd/day (WI of 46.2 and 4.6μg, respectively), well below the risk values proposed by some international organizations, even in the maximum exposure scenario. However, Pb exposure for infants and toddlers may be closer to the risk values, since milk and milk products could be the main contributor to Cd and Pb, and small children consume 2-3 times more food than adults relative to their body weight. The risk of Pb and Cd exposure through milk close to oil fields should be considered and a monitoring plan for these contaminants is strongly recommended.

Toxic heavy metals and nutrient concentration in the milk of goat herds in two Iranian industrial and non-industrial zones

“…Higher concentrations of these metals were also observed in the forage samples of the exposed area than in the control (discussed below). Similarly, Norouzirad et al (2018) reported the most important factors affecting the increase in lead and cadmium concentrations in cow's milk samples due to air pollution caused by oil extraction activity and contaminated forage. However, in addition to the contaminated environment, factors such as the period of lactation and the amount of nutrition also affect the increase in the levels of metals (Garba et al 2018).…”

“…The feed of livestock from forage and water containing heavy metals leads to intake and accumulation of these elements in the edible tissues and other products like milk (Pajohi-Alamoti et al 2017). Norouzirad et al (2018) concluded that the amount of lead metal in most cows' milk samples was higher than the acceptable limit. In other studies, the level of lead and cadmium in milk exceeded the permissible limit (Imam et al 2017;Iqbal et al 2016).…”

“…Heavy metals in milk can form a complex with nutrients such as calcium and iron and prevent their absorption by the gastrointestinal tract (Goyer 1995). The amount of heavy metals in the milk of cow (Norouzirad et al 2018), sheep (Rahimi 2013), and buffalo (Ahmad et al 2017) has been evaluated in Iran and elsewhere, but the effects of the development of gas and petrochemical industries on the quality of livestock milk are still unclear.…”

A human health risk assessment of heavy metal ingestion among consumers of protein powder supplements

“…Furthermore, milk whey (the main ingredient in whey protein powder supplements, and one of the main ingredients in weight gainer protein powder supplements) is a byproduct of cheese production, and although a direct link has not been established it is likely that contaminated milk is one of the primary contributors to heavy metal contaminated whey protein. For example, high concentrations of As, Cd, and Pb have all been detected in cow milk in different regions of the world [ 32 , 34 ]. Specifically, one study in Bangladesh reported As in cow milk at a concentration of 89.6 ± 6.5 μg/L, and noted that there was a statistically significant positive correlation between the As content in milk and the As content in the contaminated drinking water and/or straw that the cows ingested [ 32 ].…”

Concentrations of toxic elements (As, Cd, Hg and Pb) in cow milk: A review of the recent scientific literature

“…For both elements, their contents in milk samples were below the maximum permissible levels. Recently, Norouzirad et al (2018) reported the results of a study aimed at testing the hypothesis that the concentrations of Pb and Cd could be elevated in water and fodder of 14 different regions of Southwest Iran (Khuzestan province), which includes industrial and traditional farms, elevating potentially Pb and Cd pollution in the cow's milk of those regions. These areas are near petroleum extraction industries.…”