Heavy metal health risk assessment of cow’s milk from an industrialized area of Dhaka, Bangladesh

doi:10.21203/rs.3.rs-2630757/v1

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Heavy metal health risk assessment of cow’s milk from an industrialized area of Dhaka, Bangladesh

https://doi.org/10.21203/rs.3.rs-2630757/v1

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The objective of this study was to evaluate the contamination level of toxic and essential metals in milk samples with varying lactation periods (1 to 5 years) near an industrial area on the bank of Buriganga River, Dhaka, Bangladesh. Milk samples were collected and analyzed for 6 toxic metals (Cr, Ni, Pb, Hg, Cd, and As) and 5 essential (Ca, Fe, Zn, Mn, and Cu) by using wet digestion and atomic absorption spectroscopy. In this study, maximum metal contamination was detected for Ca, followed by Fe > Cr > Zn > Mn > Cu > Ni > Pb > Hg > Cd > As. The concentration of Fe, Cr, Ni, Pb, and Hg exceeded their respective national and international reference value. The potential health risk for milk consumption was investigated by estimating various exposure indices including; daily intake (EDI), Target hazard quotient (THQ), hazard index (HI), and target cancer risk (TCR). The THQ < 1 values of individual metals indicate there was no or less potential health risk due to the consumption of these milk samples. While the hazard index (HI) > 1 suggested that there might be health risk due to milk consumption. Long-time consumption of those milk samples may raise the carcinogenic risk in terms of TCR values as the TCR values of Cr, Ni, and As were obtained much higher for average consumers which exceed the maximum permeable limit (1.0×10^− 6).

Milk

Potential health risk

Health risk indices (HRI)

Target hazard quotient (THQ)

Target cancer risk (TCR)

Milk and milk-based products are considered one of the major sources of nutrients, due to the availability of proteins, fats, sugars vitamins, and minerals. Therefore, milk and milk-based products are now be considered as a vital component of human diets, especially for children and adults around the World (Buldini, Cavalli and Sharma, 2002; Qin et al., 2009). In Bangladesh, the average annual milk production is almost 683,000 tones, and the average milk consumption per person is almost 29 gm/day (Jabbar and Raha, 1984). Although milk is an ideal source of macroelements and microelements for the human body, various amounts of different toxic contaminants (toxic heavy metals) may enter into raw milk and then into the dairy products. These toxic contaminants may widely enter into the food chain through human activities or geological background (Maas et al., 2011). In some cases, the heavy metals concentration may reach harmful levels (Qin et al., 2009). Although elements such as Cd, Cu, Fe, Se, and Zn are essential elements for humans and have a variety of biochemical functions in all living organisms, elevated levels of those elements can be toxic. Other elements such as chromium (Cr) and mercury (Hg) are well known as toxic metals for human body. Extensive research has been conducted in various countries and regions for the last several decades to estimate the contamination level of heavy metals especially the toxic trace heavy metals in milk and milk-based products. (Simsek et al., 2000; Kazi et al., 2009; Bilandžić et al., 2011; Maas et al., 2011; Rahimi, 2013; Islam et al., 2021). Children are most likely to be affected given their rapid growth rate and high absorption of all elements. Among them lead (Pb), Copper (Cu), and cadmium (Cd) are considered suspect carcinogens even in low concentration in food sample. Moreover, those toxic heavy metals may causes serious adverse effects on the health such as cardiovascular diseases, kidney failure, damage of nervous system, hormonal disorders, skeletal damage and so on (Rahimi, 2013; M D Islam et al., 2020).

The elementary content of milk and milk-based products depends on several factors including environmental and genetic factors, lactation periods, nutritional status of the animal (animal food), manufacturing operations, reagent used during processing, accidental contamination including storage period and marketing processes and leaching from containers (Llobet et al., 2003; Totan and Filazi, 2020). While several studies claims that transmission of toxic heavy metals such as Cu, Pd, Hg, and Cd in to the food chain is mostly due to industrial and human activities (Maas et al., 2011; Totan and Filazi, 2020). Hazaribagh, one of the most densely populated industrial area of Bangladesh producing high quantities of metallic pollutants in air, water and soils. It has been reported earlier literature that most of the heavy metals can be taken up by the plants and are then bioaccumulated into their tissues which are further biomagnified into the grazing animals (drinking contaminated water and also by eating contaminated plants) (Chantachon et al., 2004; Miranda et al., 2005). Moreover, it is obvious that animals raised near the heavy metals contaminated area also produce contaminated milk. On the other side WHO claim, Cd, and Pb are released more frequently into the air where industrial activities are high and there may be high risk in milk of animals that are raised in that area (WHO Joint and World Health Organization., 2007).

Human health impact from exposure to toxic or hazardous chemicals via ingestion of water and food contamination may cause serious short or long-term health problems. A great deal of preventative measures have been proposed to estimate the health risks of contaminants (Wang et al., 2005). According to US EPA (1989), measurement of Target Hazard Quotient (THQ) associated with long-term exposure for individual element is a way to investigate the potential health risks (Means, 1989).

There are little reports on heavy metal contamination in milk sample in Bangladesh. Moreover, up to now there is no report has been published in literature that correlate the metal contamination level with lactation periods of cows. The aim of this study was to determine the heavy metal concentration in milk samples (both nutrients and heavy metals (i.e. Ca, Cr, Fe, Cd, Pb, Zn, Mn, Ni, Cu, As and Hg)) in various lactating period and compare them with maximum residue limit set by the regulatory authorities including EU, WHO and US EPA (World Health Organisation (WHO), 2017; United State Environmental Protection Agency (USEPA), 2022) and other data available in the literature (Zheng et al., 2007; Soares et al., 2010; Bilandžić et al., 2011; Malhat et al., 2012; Boudebbouz et al., 2021). Moreover, for the health risk assessment, several types of parameters such as estimated daily intake (EDI), health risk index (HRI), target hazard quotient (THQ), hazard index (HI), and target cancer risk (TCR) of the heavy metal’s contaminant were estimated for the purpose of safeguarding human and animal health.

2.1. Sample collection

Milk samples were collected from cows raised in select dairy farms located at Hazaribagh near the tannery industrial area from September to November 2019. A total of 50 samples were collected from distinct cows which were providing milk from 1 to 5 years (from same farm). The duration of milk providing time has been considered as lactation period in this study. If a cow is providing milk for 1 year of her life time, then it has been considered as 1st lactation period. Similarly, 2nd lactation period mean it has been providing milk for 2 years of her life time and so on. For better understanding the accumulation of heavy metals in cows, samples of different lactation period (from 1st to 5th ) have been collected. These cows were fed locally grown grass which was collected from the field near by highly polluted industrial area. 100 milliliters (ml) of milk from each cow was collected in a sanitary polyethylene container. Fresh milk was transferred to a glass bottle and immediately refrigerated where samples were stored at frozen at -20°C until analysis.

2.2. Sample preparation and analysis

In this study, the concentration of heavy metals in collected milk samples were scrutinized by initial wet digested according to modified method described by Javed (Javed et al., 2009) which was then followed by atomic absorption spectroscophic method. One gram of milk sample was taken into a 100 ml digestion vessel which was then immediately sealed. Milk samples was then digested with 10 ml of concentrated nitric acid at 200 ºC for 20 minutes. After then 5 ml of perchloric acid was added and further heated vigorously until a white fume appeared and the total volume was reduced to 2–3 ml. Finally, the total volume was brought to 50 ml by addition of deionized water. The digested samples were then filtered with 0.45 µm syringe filter. Now, all metals concentration were measured by a Perkin-Elmer flame atomic absorption spectrometer (Model-An Analyst 800, USA).

2.3. Quality control and quality assurance

Adequate precautions were taken to assure the reliability and reproducibility of the results. The reagents were of analytical grades. Calibration standards for all individual metals were performed by using high purity grade commercial metal standards (Merck, Germany) for atomic absorption analysis. A recovery test was conducted for all the metal samples by spiking the analyzed samples with aliquots of standard of the respective metals and then the concentrations of the samples were analyzed. All the metals show the recovery percentage within a range of 90–95%.

The human health risks assessment was calculated based on the average and highest heavy metal concentration in lactating cow milk sample. For that purpose, estimated daily intake (EDI), health risk index (HRI), target hazard quotient (THQ), hazard index (HI), target cancer risk (TCR) were investigated. Moreover, the contamination level was also compared with published literature data and also with permeable limit set by different international and national regulatory authorities (Food and Agriculture Organization (FAO) and World Health Organisation (WHO), 2004). The health risk assessment parameters including EDI, HRI, THQ, HI, TCR were measured using the following formulas (Saha and Zaman, 2013; Md Didarul Islam et al., 2020):

\(\text{E}\text{D}\text{I}=\frac{{\text{C}}_{\text{m}}\times \text{F}\text{I}\text{R} \times \text{E}\text{F}\times \text{E}\text{D}}{\text{B}\text{W}\times \text{A}\text{T}}\)	(1)
\(\text{H}\text{R}\text{I}=\frac{\sum ({\text{C}}_{\text{m}}\times \text{F}\text{I}\text{R})}{\text{R}\text{f}\text{D}\times \text{B}\text{W}}\)	(2)
\(\text{T}\text{H}\text{Q}=\frac{\text{E}\text{F}\text{r}\times \text{E}\text{D}\times \text{F}\text{I}\text{R}\times {\text{C}}_{\text{m}}}{\text{R}\text{f}\text{D}\times \text{B}\text{W}\times \text{A}\text{T}}\)	(3)
\(\text{H}\text{I}=\sum \text{T}\text{H}\text{Q}\)	(4)
\(\text{T}\text{C}\text{R}=\frac{{\text{C}}_{\text{m}}\times \text{E}\text{F}\text{r}\times \text{E}\text{D}\times \text{F}\text{I}\text{R}\times \text{C}\text{P}\text{S}}{\text{B}\text{W}\times \text{A}\text{T}}\)	(5)

where C_m = concentration of metal in mg/l; FIR (food ingestion rate) = 0.200ml/day daily average milk consumption by a person; EF (exposure frequency) = 365day/yr; ED (exposure duration) = 70 year equivalent to avg. life time in Bangladesh; BW (body weight) = 60kg; AT (average time) = (365\(\times\) 70) day (Saha and Zaman, 2013; Meshref, Moselhy and Hassan, 2014); R_fD = reference dose safe level of exposure by oral for life time (Cui et al., 2004; Li et al., 2010, 2012; Singh et al., 2010; Pandey, Shubhashish and Pandey, 2012); THQ is the target hazard quotient; EFr is the exposure frequency (365 day per yr); CPS is the oral carcinogenic slope factor (mg/l/day)⁻¹; CPS values of Cr, Ni, As, and Pb were 0.5, 1.7, 1.5, and 0.0085 (mg/l/day)⁻¹ respectively (United State Environmental Protection Agency (USEPA), 2022).

4.1. Heavy metals concentration in milk samples

The targeted heavy metals concentration (Ca, Fe, Cr, Zn, Mn, Cu, Ni, As, Cd, Pb, and Hg) in different cow milk samples (different lactation period (1st − 5th years)) collected in this study were tabulated in Table 1. From Table 1 it was observed that average concentration gradually increased with increasing lactation period (except Cu). Maximum metal contamination was detected for Ca that was followed by Fe > Cr > Zn > Mn > Cu > Ni > Pb > Hg > Cd > As. The mean Ca, Fe, Cr, Zn, Mn, Cu, Ni, As, Cd, Pb and Hg concentration were 1195 (889–1372 mg/l), 6.56 (4.5–9.31 mg/l), 6.38 (3.51–8.59 mg/l), 3.77 (1.59–9.31 mg/l), 0.27 (0.11–0.5 mg/l), 0.12 (0.02–0.36 mg/l), 0.11 (0.02–0.24 mg/l), 0.01 (0-0.3 mg/l), 0.03 (0-0.05 mg/l), 0.11 (0.03–0.22 mg/l) and 0.06 (0-0.11 mg/l) mg/l respectively which is shown in the Table 1 and Figs. 1 & 2.

Table 1

Comparison of different heavy metals concentration with their reference concentration (*n = 10*)
Metal	Average metal concentration in the lactation period of cow milk (mg/l)					Average (mg/l)	Metal concentration range found in Cow’s milk (from literature) (mg/l)
Metal	1st	2nd	3rd	4th	5th	Average (mg/l)	International	Bangladesh
Ca	889.2	1132.9	1281.2	1302.7	1371.8	1195.56	1043–1701 (Simsek et al., 2000; Hunt and Nielsen, 2009)	542–1583 (Khan et al., 1989)
Fe	4.5	4.92	6.02	8.06	9.31	6.56	1.13–16.38 (Malhat et al., 2012; Lutfullah et al., 2014)	0.064–0.631 (Muhib et al., 2016)
Mn	0.12	0.11	0.23	0.41	0.5	0.27	0.02–0.07 (Hunt and Nielsen, 2009; Pilarczyk et al., 2013)	0.092–0.130 (Muhib et al., 2016)
Zn	1.59	2.42	3.8	4.91	6.12	3.77	0.0247-18.3 (Licata et al., 2004; Malhat et al., 2012; Meshref, Moselhy and Hassan, 2014)	0.1-1.002 (Jolly et al., 2017)
Cu	0.02	0.08	0.07	0.09	0.36	0.12	0.039–37.29 (Lutfullah et al., 2014)	0.064-2.3 (Islam et al., 2015; Muhib et al., 2016)
As	0	0	0.01	0.02	0.03	0.01	0.025-0.10 (Simsek et al., 2000; Licata et al., 2004)	0.097–1.08 (Shaheen et al., 2016)
Cd	0	0	0.02	0.05	0.1	0.03	0.001–4.06 (Malhat et al., 2012; Totan and Filazi, 2020)	0.024–0.054 (Islam et al., 2015; Muhib et al., 2016)
Pb	0.03	0.03	0.06	0.12	0.22	0.09	0.018–7.015 (Malhat et al., 2012)	0.012-0.2 (Islam et al., 2015; Muhib et al., 2016)
Ni	0.02	0.07	0.11	0.12	0.24	0.11	0.318–0.484 (Coni et al., 1994, 1995)	0.071–0.085 (Jolly et al., 2017)
Cr	3.51	4.5	7.15	8.14	8.59	6.38	0.0008–0.175 (Totan and Filazi, 2020)	0.373-1.6 (Islam et al., 2015; Muhib et al., 2016)
Hg	0.01	0.03	0.07	0.09	0.11	0.06	0.0025–0.005 (Simsek et al., 2000; Caggiano et al., 2005; Bilandžić et al., 2011)	0.006–0.03 (Jolly et al., 2017)

Table 2

Estimation of different heavy metals’ EDI value from TDI value in milk sample.
Element		TDI Value (mg/day bw/day)				Estimated daily intake (EDI) (mg/day/kg bw)		EDI value from TDI value (%)
Element		TDI Value (mg/day bw/day)				EDI_mean	EDI_max	% TDI_mean	% TDI_max
NUTRIENT
	Ca		694^*	3.7683			4.5727	0.543	0.659
	Fe		0.8^*	0.0230			0.0310	2.875	3.875
	Mn		11.0^*	0.0010			0.0017	0.009	0.016
	Zn		60^**	0.0129			0.0204	0.022	0.034
	Cu		30^**	0.0006			0.0012	0.002	0.004
TOXIC
	As		0.12^**		0.0001		0.0001	0.083	0.083
	Cd		0.06^**		0.0002		0.0003	0.333	0.500
	Pb		0.21^**		0.0004		0.0007	0.191	0.333
	Ni		0.3^**		0.0004		0.0008	0.133	0.267
	Cr		0.034^**		0.0202		0.0286	59.412	84.118
	Hg		0.043^**		0.0002		0.0004	0.465	0.932
^* Dietary Reference Intakes for Japanese, 2010 ^** Evaluations of the Joint FAO/WHO Expert Committee on Food Additives (JECFA), 2019

Table 3

Target hazard quotient (THQ) values of heavy metals from milk for average and high adult consumers in Bangladesh.
Toxic elements	RfD (mg/l/day)	THQ		CPS (mg/l/day)⁻¹	TCR (×10^− 4)
Toxic elements	RfD (mg/l/day)	High consumer	Average consumer	CPS (mg/l/day)⁻¹	High consumer	Average consumer
Ca	33.3 (Goldhaber, 2003)	0.137	0.113	-	-	-
Fe	0.64 (Goldhaber, 2003)	0.048	0.036	-	-	-
Cr	1.5 (Ahmed et al., 2015)	0.012	0.007	0.5 (United State Environmental Protection Agency (USEPA), 2022)	143	101
Zn	0.3 (Ahmed et al., 2015)	0.068	0.043	-	-	-
Mn	0.14 (Goldhaber, 2003)	0.030	0.016	-	-	-
Cu	0.04 (Ahmed et al., 2015)	0.333	0.167	-	-	-
Ni	0.0036 (Ahmed et al., 2015)	0.333	0.167	1.7 (United State Environmental Protection Agency (USEPA), 2022)	13.6	7.36
As	0.0003 (Vieira et al., 2011)	0.183	0.104	1.5 (United State Environmental Protection Agency (USEPA), 2022)	1.5	0.75
Cd	0.001 (Vieira et al., 2011)	0.222	0.120	-	-	-
Pb	0.004 (Vieira et al., 2011)	0.019	0.013	0.0085 (United State Environmental Protection Agency (USEPA), 2022)	0.062	0.035
Hg	0.0003 (Vieira et al., 2011)	1.222	0.667	-	-	-
HI		2.609	1.453	Total TCR	158.162	109.145

4.2. Health risk assessment

Health risks of the local milk consumers were first assessed by comparing EDI and tolerable daily intake (TDI). The mean EDI of each metal were calculated from Eq. (1) which is based on the average and maximum concentration of each individual heavy metal from samples collected from cows with different lactation period (1st -5th years). It is observed in the Table 2 that EDI values of all heavy metals are less than TDI value and maximum TDI percentile are found in chromium.

Table 3 summarizes the exposure assessment and comparison of metals with R_fD values in the study area. Target hazard quotient (THQ) for high consumers and average consumers were calculated from each metal high and average concentration in samples from different lactation period (Table 3). In this study, THQ value for each metal ranges from 0.012 to 1.222 for highest consumers and 0.007 to 0.667 for average consumers and HI values were assessed 2.690 and 1.453 for highest and average consumption respectively.

According to the US Environmental Protection Agency (US EPA) and the International Agency for Research on Cancer (IARC), Cr, Ni and As are considered to be known human carcinogens whereas Pb has been proven as probable human carcinogen (Tchounwou et al., 2012; US EPA, 2022). This is why, TCR values of these metals were calculated using Eq. 5 and the results were summarized in Table 3. The target cancer risk (TCR) values in accordance highest metal consumer for Cr, Ni, As, and Pb are 143 × 10^− 4, 13.6 × 10^− 4, 1.5 × 10^− 4, and 6.2×10^− 6, respectively while with average metal consumer for Cr, Ni, As, and Pb are 101 × 10^− 4, 7.36 × 10^− 4, 7.5 × 10^− 5, and 3.5×10^− 6, respectively. In both cases, for highest and average consumer, metal consumption has for each individual metal was found higher then safe limit of 1 ×10^− 6 set by USEPA.

5.1. Heavy metals concentration in milk samples

The concentration of essential and toxic metals in this study along with estimated other international and Bangladesh values are summarized in Table 1. It is observed that the concentration of each of the metals increases with the cow’s lactation period from 1st to 5th. This seems to suggest that as cows age, the bioaccumulation of all the minerals studied increases in its milk. Several researches have reported bioaccumulation of essential or toxic metals in many different organs of livestock such as kidney, lever, meat, brain, milk, egg, etc (Tomza-Marciniak et al., 2011; Shen, Chi and Xiong, 2019). Milk is a complex composition of water, minerals, vitamins, immune-globulins, caseins, fats, etc. Different organs of the cows are involved in the production of this lactation product (Meshref, Moselhy and Hassan, 2014). This may be the reason of increase in mineral composition of milk with age of the cows.

Among the essential minerals tested, Ca was found highest in concentration in the milk samples. Ca is a very important mineral in milk, so, farmers used to give Ca rich supplement in Cows. The enrichment of Ca concentration in the milk samples may be due to the presence of Ca in cows’ feeds. However, the mean concentration of Ca in the milk samples was around 1195 mg/l which is within the permeable limit set for Ca in drinking water (World Health Organization, 2003). The concentration of Fe and Cu were also found significantly high in the samples. The high Fe content may be due to the existence of high amount of Fe in the surface water and soil of the local area or leaching from industrial activities (Karim et al., 2013). However, Fe can represent a problem in dairy technology because of its catalytic effect on oxidation of lipids with development of unpleasant smell, bounding preferably proteins and membrane lipoproteins of milk fatty globule (González-Montaña et al., 2012; Najarnezhad et al., 2015). Cu in the milk samples may come from the local surface water. Few essential minerals like Zn, Mn, Ca, Cu can adsorb few heavy metals on to them (Djukić-Ćosić et al., 2006). Thus, a little increase of the essential elements can help to reduce the contamination of cows’ milk from some toxic elements.

In this study, concentration of Cr (6.38 mg/l) was found to be significantly higher than the reference value (0.02–0.29 mg/l) (Póti et al., 2021) and also maximum permeable limit of 0.02 mg/l (Food and Agriculture Organization (FAO) and World Health Organisation (WHO), 2004). The presence of high chromium concentration was due to the establishment of a number of leather industries in local Hazaribagh area. The local tanning industries use excess amount of Cr(III) salts during tanning process which were directly or indirectly contaminated the local area (Chowdhury et al., 2015). There is chance of transfer of the pollutant minerals to local vegetations and plants. The cows raised in that locality are used to take locally grown grass as a portion of their feeding. This is probably the route of high Cr contamination from tannery waste to vegetations and then to locally raised cows and finally into cows’ milk.

In the milk samples, a substantial amount of Pb, Hg, Cd, Ni, As were detected and their concentration were gradually increase with increasing the animal age which can be explained by as increasing the animal age leads to the accumulation of individual element into the animal body (Najarnezhad et al., 2015). Several studies suggested the contamination level is depends on so many factors including industrial activities, climate factors, regional area, accumulation along the roads and motorways, agricultural wastes and so on. In this study, the studied area was nearby highly contaminated industrial and populated area composed of battery manufacturing industries, lead smelting industries and dumped non-usable and rejected battery wastes to the local environment (Md Didarul Islam et al., 2020; Islam et al., 2022). Moreover, it should be noted that more than 50% milk samples were reported to be very low concentration (below detection limit) of As, Hg, and Cd.

5.2. Health risk assessment

Health risks due to the consumption of milk samples were firstly assessed by comparing EDI and tolerable daily intake (TDI). The mean EDI of each metal was calculated from Eq. (1) which is based on average and maximum concentration of each individual heavy metal from samples collected from cows with different lactation period (1st − 5th years). In this study, the values of TDI (mg/l/day) were collected from TDI values reported in the Evaluations of the Joint FAO/WHO Expert Committee on Food Additives (JECFA) (World Health Organization, 2019). TDI is not nessesserily expresed as TDI but other terms like PMTDI (Provisional Maximum Tolerable Daily Intake). However, TDI values of Ca, Mn and Cr are not set by any guidelines, for those reason RDA (Recommended Dietary Allowances) values of Cr and Ca and UL (Tolerable Upper Intake Level) for Mn are used for comparison that are set by Dietary Reference Intakes for Japanese (Morita et al., 2013).

The percentages of EDI to TDI were calculated for five essential metals (Table 2). The mean and maximum estimated daily intake of calcium, iron, manganese, zinc and copper were less than their respective TDI value. Among these five metals iron, manganese and zinc poses both positive and toxic effect to human body but in terms of toxicity, the EDI of these three metals were less than 4% of the TDI, and iron shows maximum percentile TDI (3.875%). Therefore, it can be concluded that the local people may consume more of these heavy metals via intake of those milk samples.

Arsenic, nickel, lead, chromium, cadmium, and mercury were considered to be toxic metals and daily intakes of each metal were summarized in Table 2. In terms of toxicological aspects, the mean and maximum EDI values of arsenic, cadmium, lead, nickel and mercury were far below the TDI level (< 1%). But mean and maximum EDI value of chromium was found 59.412 and 84.118% which is close TDI level. This is due to the presence of high number of leather industries in the vicinity. These industries use chrome salts for leather processing and dump their waste mostly without any treatment in the nearby Buriganga River (Md Didarul Islam et al., 2020). Thus, it is not recommended that to drink much milk from those locations where samples were collected (nearby) in terms of highly chromium contamination and government should set up a strict guideline for tannery waste disposal system and it should be regularly monitored.

According to US EPA (Means, 1989), when THQ of any metal and HI of all metals present in any sample are individually less than 1, then the consumption of that material by human will be considered as safe for human body. In the present study THQ of each studied metals due to consumption of the milk samples was found less than 1 but the total THQ represented as HI is greater than 1 in both average and high consumers (Table 3). The HI values between 1 to 10, indicating there may be moderate hazard due to the consumption of this food (Lemly, 1996). In one study Zheng et al. exhibited HI values of 2.1, and 2.89 for Cu, and Ni respectively in Botswana of Africa (Zheng et al., 2007). Thus, indicating there might be noticeable moderate hazard due to the consumption of those metals. In our study, HI values were almost similar results (range between 1.453–2.609), indicating similar health hazard problem due to the consumption of milk sample. In addition, from Table 1 it can be seen that higher amount of heavy metal was found concentrated in cows which had been lactating milk for a long time. So, it can be concluded that milk collected from those old cows prone to cause higher health risk.

According to International Agency for Research on Cancer (IARC), Ni, Cr, As (Known) and Pd (Probable) are considered to be potential carcinogenic element (Tchounwou et al., 2012). Thus, it is obvious that food containing those selected contaminant may be responsible for carcinogenic risk. In this study, probable carcinogenic risk due to long term consumption for lifetime target carcinogens risk (TCR) and total cancer risk (Total TCR) were calculated and the results were summarized in Table 3. According to NYDOH, TCR values less then 10^–6 indicates low cancer risk, TCR values lie between 10^–5 to 10^–4 notify moderate level of cancer risk, and TCR values ranging from 10^–3 to 10^–1 imply high risk of causing cancer (Ashraf et al., 2021). The calculated TCR values for Cr, Ni, As and Pb were significantly higher than the acceptable carcinogenic risk limit (1.0 × 10^− 6) for any metal for both high and average consumers. The TCR values of Cr and Ni for milk sample lies between 10^–3 to 10^–1, indicating high cancer risk due to the consumption of those milk sample. On the other hand, TCR values for As was found to be 1.5 × 10^− 4 and 7.5 × 10^− 5 for higher and average consumer, that indicating moderate human cancer risk. TCR values of 6.2 × 10^− 6 and 3.5 × 10^− 6 As for higher and average Pb consumer, these relate to the low cancer risk. Total TCR > 1 in ten thousand representing there may be low public health risks and require additional information whereas Total TCR > 10^–3 indicating moderate public health risks (Li and Zhang, 2010). In this study total TCR > 10^–3, which would cause moderately increased risk of cancer due to the ingestion of milk sample over a long-life time.

The heavy metals’ concentrations of milk samples collected from varying lactation periods of different cows were investigated. Though in this study a small amount of 50 samples were examined but inferences drawn on the results were carefully revised and reported. The collected cow’s samples were from one same farm with different birth period and it was not possible to get a control sample as there was no farm on that area where cows were raised free from all sorts of contaminations which causes a limitation to this study. However, study revealed that bioaccumulation of mineral contaminants in cows is apparent. Thus, toxic minerals can cause severe biochemical adverse effects primarily to the cows and secondarily to the human bodies after consumption those cows’ milk. Milk is a nutritious food to human body. The EDI of the locally produced cows’ milk may not cause immediate health risk to the consumers; however, after long-time consumption of the milk, it may become hazardous to humans; mostly due to the Cr contamination. Cr, Ni, As, and Pd contamination in the milk samples exceed the maximum permeable limit of TCR value. This suggests that the sources of these contaminations to the local environment need to be soften. Two well-known sources of contamination in Hazaribagh are tannery effluents and battery smelting industries. Untreated effluents and wastes from these two industries are directly contaminating the soil, vegetations, aquatic lives of the local environment and indirectly contaminating the livestock and people of that area through their food chain. Environmental remediation and/or public health interventions may be needed to reduce this exposure. Government institutions may need to strengthen national regulations and establish monitoring efficient procedures for controlling the heavy metal pollution to the environment.

Conflict of interest

The authors declare that they have no conflict of interest.

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Heavy metal health risk assessment of cow’s milk from an industrialized area of Dhaka, Bangladesh

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Abstract

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1. Introduction

2. Materials And Methods

2.1. Sample collection

2.2. Sample preparation and analysis

2.3. Quality control and quality assurance

3. Health Risk Assessment

4. Result

4.1. Heavy metals concentration in milk samples

4.2. Health risk assessment

5. Discussion

5.1. Heavy metals concentration in milk samples

5.2. Health risk assessment

6. Conclusion

Declarations

References

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