Milk is nearly a perfect natural food and is widely used by all segments of our population especially for infants and the elderly. Organochlorine pesticides (OCPs) have been used worldwide, particularly in many African countries as in Egypt for the control of pests. OCPs are characterized by their bioaccumulation in the environment, especially in the food chain, where they find their way into the human body. The objectives of this study were initially to estimate the residual concentrations of different OCPs in three kinds of fresh and raw milk from different animals (cattle, buffalo, and goat) marketed in Egypt. Additionally, human dietary intake and risk assessment of OCPs were calculated. The tested OCPs included pp-DDT and its metabolites pp-DDD and pp-DDE; hexachlorohexanes (HCHs) including
Milk is a complex, bioactive substance to promote growth and development of infant mammals. Cow, buffalo, and goat milk are widely consumed around the world, especially in Egypt. In fact, milk is considered as an ideal source of macroelements such as calcium, phosphorus, and potassium [
The widespread occurrence of any foreign chemical in the environment is a matter of public health concern. Pesticides are extensively used to increase agricultural products through preventing losses due to agricultural pests. The health authorities also use these chemicals to control various vectors, which spread diseases like malaria and plague [
Among the major groups of pesticides, organochlorines are more potent due to their persistence and stability. Universally important organochlorine pesticides (OCPs) are para, para, dichlorodiphenyltrichloroethane (pp-DDT), hexachloride benzene (HCB), chlordane, heptachlor, aldrin, dieldrin, and endrin. Due to the lipophilic nature of these pesticides, milk and other fat-rich substances are the key items for their accumulation [
Egypt as one of the most populous countries in Africa depend mainly on agricultural activities as major sources of national income. Therefore, pesticides are frequently used in Egypt to control pests or directly spread into animal skin for prevention and control of external parasites. These chemicals may find their way into animal body and subsequently pass into milk causing several toxicological implications for both animal and human if contaminated milk or other dairy products were consumed [
Due to the previous facts, this study was conducted to firstly investigate the residual concentrations of OCPs in the milk of cattle, buffalo, and goat in Egypt. The tested OCPs included pp-DDT and its metabolites pp-DDD and pp-DDE; hexachlorohexanes (HCHs) including
All experiments were done according to the rules and guidelines of Zagazig University, Egypt.
Sixty milk samples (20 each of cow, buffalo, and goat milk) were randomly purchased from markets in Zagazig city, Sharkia province, Egypt. Raw milk is sold in Egypt in polyethylene bags, and each sample weighs 500 g. Samples were transferred into laboratory in a cooled container. Organochlorine pesticides were extracted and measured at Agricultural Research Center, Dokki, Giza, Egypt.
Standard OCPs including pp-DDT, pp-DDD, pp-DDE,
Each individual sample (50 ml) was mixed with anhydrous sodium sulfate (100 g) and petroleum ether (150, 100, and 100 ml, respectively) in three successive extraction steps for 2 min each, as described before [
Partitioning of the extracted samples was carried out according to the method of the Association of Official Analytical Chemists [
Cleanup of the extracted samples, to remove the residual fat, was performed by transferring the extract into a glass chromatographic column (22 mm i.d.) containing 20 g activated florisil (60–100 mesh) topped with 1-cm layer of anhydrous sodium sulfate. The prepared column was firstly rinsed with 50 ml petroleum ether, and then the extracted sample was transferred onto the column. The column was eluted with 200 ml eluent (10% anhydrous diethyl ether + 90% petroleum ether) followed by a second elution with 100 ml of another eluent (1% acetonitrile + 29% n-hexane + 70% methylene chloride). The collected eluent was concentrated on a rotary evaporator and dissolved in hexane to a volume of 10 ml. An aliquot of each extract was transferred to 2-ml injection vials to be ready for the analysis with the electron capture gas chromatography.
Organochlorine residues were determined by analysis of samples using electron capture gas chromatography (Hewlett Packard GC Model 6890) equipped with Ni63–electron capture detector. GC conditions were HP- 5MS capillary column (30m length X 0.32mm internal diameter (i.d..), X 0.25
Calibration standard curves were created and the organochlorine pesticide residues were quantitatively determined by comparison with the standard solutions injected under the identical gas chromatography conditions. The standard reference material, SRM 1947 (Lake Michigan Fish Tissue), was analyzed during the analysis of samples followed by the same procedure of extraction, cleanup, and analysis. The percentage of recoveries of the organochlorines tested ranged from 86% to 109%. Residue levels for each pesticide were subsequently corrected for the recovery values. The limits of detection (LOD) and quantification (LOQ) for the tested OCPs were based on 3:1 signal to noise ratio (S/N) and ranged from 0.004 to 0.20 ng g−1 (LOD) and 0.024 to 0.036 ng g−1 (LOQ).
To estimate human health risks due to ingestion of OCPs contaminated milk among Egyptian populations (children and adults), both estimated daily intake (EDI) and hazard ratio (HR) were calculated based on the equations recommended by USEPA [
Noncancer and cancer risk assessment were calculated using hazard ratio (HR). A hazard ratio higher than one indicates potential human health risks [
The benchmark concentration (BMC) for carcinogenic effects was derived from cancer slope factor (CSF) and for noncarcinogenic effects was based on the oral reference dose (RFD). Both CSF and RFD were obtained from the United States Environmental Protection Agency Integrated Risk Information System [
All values are expressed as means ± SE, and all measurements were carried out in duplicate. Statistical significance was evaluated using the comparative of means method (the Tukey–Kramer HSD test) (JMP statistical package; SAS Institute Inc., Cary, NC).
Organochlorine pesticides (OCPs) have been used worldwide, particularly in Africa for several decades. Although many are banned, several African countries still use OCPs especially for the prevention and control of malaria. OCPs are characterized by their bioaccumulation in the environment, especially in the food chain, where they find their way into the human body.
In this study, the residual concentrations of different OCPs in three kinds of marketed milk (cattle, buffalo, and goat) in Egypt were estimated.
The recorded results revealed that goat and buffalo milk samples had the highest contamination level of OCPs (75%, 15 out of 20 examined samples), while this percentage was 50% (10 out of 20 examined samples) in cow’s milk (see Figure
Frequency (%) of individual and total OCPs contamination of the examined milk samples from different animal species (n=20 each).
The mean values of ΣOCPs in the examined milk samples were 317.83 ± 34.11, 605 ± 50.54, and 1210.57 ± 99.55 (ng/g ww) in the examined cattle, buffalo, and goat milk samples, respectively (see Figure
Although OCPs’ use has been banned in Egypt since the 1980s, DDTs are still detected in various foods in the country. For instance, mussels from Abu Qir Bay contained several OCPs, with DDT concentrations up to 31000 (ng/g dw), but a risk assessment showed no expected adverse effects on people through mussel consumption [
Hexachlorocyclohexanes (HCHs) were detected in 30%, 35%, and 65% of the examined cattle, buffalo, and goat milk samples, respectively (see Figure
Furthermore, the concentrations of HCHs in this study were comparable to the recorded concentrations in cattle raw milk marketed in Egypt, India, Ghana, Mexico, and Uganda [
Heptachlor and its epoxide were detected in 35%, 35%, and 50% of the examined cattle, buffalo, and goat milk samples, respectively (see Figure
Drins either aldrin or endrin were detected in 50%, 60%, and 75% of the examined cattle, buffalo, and goat milk samples, respectively (see Figure
Other examined OCPs such as chlordane, HCB, and methoxychlor were detected in 10-60% (see Figure
It is worth noting that in the present work goat milk had the highest OCPs residues. This may be due to the grazing behavior of the goat. Additionally, buffalo’s milk had higher OCPs compared with the milk of the cow. This may be attributed either to the high fat content (7.47%) of the buffalo’s milk or to the dietary habits of the buffalo, like different fodder and to variations in diets compared with the cows [
Humans can be exposed to OCPs via several routes including breathing of polluted air, dermal penetration, or ingestion of contaminated foods and drinking water. OCP-contaminated foods like milk and other dairy products are considered the main source of human exposure to pesticides [
Estimated daily intake of OCPs due to ingestion of milk among Egyptian population.
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| 10000 | 74.03 | 296.13 | 184.43 | 737.73 | 293.7 | 1174.8 |
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| 10000 | 51.1 | 204.4 | 70.36 | 281.46 | 184.1 | 736.4 |
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| 10000 | 57.43 | 229.73 | 120.73 | 482.93 | 147.16 | 588.66 |
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| 100 | 42.23 | 168.93 | 50.76 | 203.06 | 45.16 | 180.66 |
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| 100 | 64.03 | 256.13 | 78 | 312 | 51.1 | 204.4 |
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| 5000 | 50.7 | 202.8 | 60.53 | 242.13 | 307.2 | 1228.8 |
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| 5000 | 111.46 | 445.86 | 317.03 | 1268.13 | 736.66 | 2946.66 |
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| 100 | 38.86 | | 61.83 | | | |
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| 100 | 7.66 | 30.66 | 24.66 | 98.66 | 51.06 | |
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| 500 | 47.36 | 189.46 | 40.33 | 161.33 | 41.46 | 165.86 |
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| 600 | 11.83 | 47.33 | 24.8 | 99.2 | 37.76 | 151.06 |
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| 6300 | 5.16 | 20.66 | 15 | 60 | 29.6 | 118.4 |
ADI: acceptable daily intake.
Values in bold are higher than ADI.
The analyzed OCPs in the present study had both cancer and noncancer risks [
Noncancer hazard ratio among Egyptian population due to ingestion of OCPs-contaminated milk from different animal species.
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| 5.00E-04 | 0.04 | 0.15 | 0.09 | 0.37 | 0.15 | 0.59 |
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| 5.00E-04 | 0.03 | 0.1 | 0.04 | 0.14 | 0.09 | 0.37 |
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| 5.00E-04 | 0.03 | 0.11 | 0.06 | 0.24 | 0.07 | 0.29 |
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| 5.00E-04 | 0.02 | 0.08 | 0.03 | 0.1 | 0.02 | 0.09 |
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| 5.00E-04 | 0.03 | 0.13 | 0.04 | 0.16 | 0.03 | 0.1 |
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| 3.00E-04 | 0.02 | 0.06 | 0.02 | 0.07 | 0.09 | 0.37 |
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| 3.00E-04 | 0.03 | 0.13 | 0.09 | 0.38 | 0.22 | 0.88 |
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| 3.00E-04 | 0.01 | 0.05 | 0.02 | 0.07 | 0.04 | 0.18 |
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| 3.00E-04 | 0.002 | 0.01 | 0.01 | 0.03 | 0.02 | 0.06 |
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| 5.00E-04 | 0.02 | 0.09 | 0.02 | 0.08 | 0.02 | 0.08 |
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| 8.00E-04 | 0.01 | 0.04 | 0.02 | 0.08 | 0.03 | 0.12 |
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| 0.05 | 0.26 | | 0.75 | | | |
RFD: oral reference doses.
Values in bold represent higher hazard ratio (>1.0).
Cancer hazard ratio among Egyptian population due to ingestion of OCPs-contaminated milk from different animal species.
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| 0.34 | 0.22 | 0.88 | 0.54 | | 0.86 | |
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| 0.24 | 0.21 | 0.85 | 0.29 | | 0.77 | |
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| 0.34 | 0.17 | 0.68 | 0.36 | | 0.43 | |
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| 4.5 | 0.01 | 0.04 | 0.01 | 0.05 | 0.01 | 0.05 |
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| 4.5 | 0.01 | 0.06 | 0.02 | 0.07 | 0.01 | 0.05 |
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| 1.1 | 0.05 | 0.18 | 0.06 | 0.22 | 0.28 | |
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| 1.1 | 0.1 | 0.41 | 0.29 | | 0.67 | |
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| 17 | 0.002 | 0.009 | 0.004 | 0.015 | 0.01 | 0.03 |
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| 17 | 0.0004 | 0.002 | 0.001 | 0.006 | 0.003 | 0.01 |
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| 0.35 | 0.14 | 0.54 | 0.115 | 0.46 | 0.12 | 0.47 |
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| 1.6 | 0.01 | 0.03 | 0.02 | 0.06 | 0.02 | 0.09 |
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| NA | NA | NA | NA | NA | NA | NA |
CSF: cancer slope factor.
NA: not available as there is no CSF value for methoxychlor.
Values in bold represent higher hazard ratio (>1.0).
Maternal transfer is also possible across the placenta to the foetus or via breast milk to infants. Residue levels of these compounds in living organisms depend on each organism’s habitat and position in the food chain [
In conclusion, high concentration of the tested OCPs reveals the increased improper use of these pesticides by the farmers for agricultural purposes. These pollutants are characterized by long persistence in the environment and thus may pass to next generations of humans and different plant and animal species. Thus, continuous monitoring studies to investigate the status of OCPs contamination in the Egyptian environment and food subjects are mandatory in Egypt.
The data used to support the findings of this study are available from the corresponding author upon request.
The authors declare that they have no conflicts of interest.
The authors would like to thank Food Control Department, Faculty of Veterinary Medicine, Zagazig University for their kind support during conducting this study.