INVESTIGATION OF HEAVY METALS IN WATER AND DAIRY MILK OF GREATER CHITTAGONG DISTRICT OF BANGLADESH

Abstract

The presence of heavy metals (copper, lead, nickel etc.) in water as well as dairy milk is a common problem in Bangladesh. No systematic study has previously been attempted for investigation of heavy metals both in water and milk which could pose threats to public health. Therefore, a cross sectional study was conducted on different water sources and dairy milk of greater Chittagong in Bangladesh. The overall objective of the study was to assess the status of the selected heavy metals in water and dairy milk, identify risk factors and evaluate possible public health risk. A total of 108 water samples (72 tube well and 36 tap water) and 96 dairy milk samples, along with epidemiological and ecological data were obtained from the selected study sites and evaluated the samples obtained by Atomic Absorption Spectrometry during December 2013-May 2014. The prevalence of heavy metals in tap water was zero for lead, nickel and copper in the present study. The overall prevalence of lead was higher in tube well water (37.5%) than milk (6.3%). The prevalence of lead in tube well water of Chittagong was significantly higher (61.1%) than in Chandpur (13.9%) but lower in dairy milk in Chittagong (4.2%) than in Chandpur (8.3%). The prevalence of nickel was detected both in tube well water and dairy milk at high prevalence (30.6-37.5%) in Chandpur. Contrarily, nickel was detected only in dairy milk at high rate of prevalence (27.1%) in Chittagong. Around 45% of lead positive water samples (N=56) and 26% of lead positive dairy milk samples (N=51) crossed the reference values (reference values: 0.05 mg/L and 0.49 mg/L for water and dairy milk, respectively). Milk samples obtained from Chittagong crossed the reference value of lead had high frequency (44.8%). Fisher’s exact test followed by a univariable logistic regression was applied to identify potential risk factors associated with lead and nickel in dairy milk. Site, area and industry were identified risk factors for lead in dairy milk (OR= 4.6: Chittagong versus Chandpur; OR=16.7: semi urban versus rural and OR=14.7: semi urban versus urban; OR=4.5: industry present versus industry absent). Area and presence of industry were determined risk factors for nickel in dairy milk (OR=5.4: semi-urban versus rural; OR=2.0: industry versus non-industry). Thirty one percent of nickel positive tube well water (N=18) also crossed the reference value in this study. Tube well water samples obtained from Chittagong crossed the reference value of lead had higher frequency (95.5%) than in Chandpur (13.9%). The presence of lead and nickel in tube well water and dairy milk at high concentration that crossed the reference values is certainly posing animal and public health threat such as causing haematotoxicity, neurotoxicity, genotoxicity, reproductive toxicity etc. Therefore, possible techniques to reduce the risk level of heavy metals in tube well water and dairy milk along with public awareness should be sought in the study areas.