Background. Objectives

Transcription

1 BRIEFING PAPER Contaminated irrigation water and food safety for the urban and peri-urban poor: appropriate measures for monitoring and control from field research in India Fiona Marshall, University of Sussex Ravi Agarwal, Toxics Link Chandrachur Ghose, University of Sussex Abhay Kumar, Toxics Link Madhoolika Agrawal, Banaras Hindu University D S Bhupal, Delhi University October 2006

2 Background In a rapidly urbanising world, where there is increasing concern about the shortage of fresh water, the practice of using wastewater for irrigation of food crops in urban fringe (peri-urban) areas is often encouraged. However, whilst in many cases this may be an appropriate thing to do, it is important to be able to support local communities and authorities to consider the true costs and benefits of this type of practice. One potential risk of wastewater use is the contamination of food as a result of industrial pollution. This contamination can have serious implications for the health and livelihoods of those that consume produce that was grown with wastewater irrigation, and for the poor in particular. There are various things that can be done, either to reduce pollution at source, or in some cases, to ameliorate the impact of the pollution, but most rely on understanding and cooperation between various agencies and with the local community. In current policy and practice there is little recognition of the link between industrial pollution and food safety or of the measures (across a wide range of policy fields) that could help to understand and address this. This project builds on our previous DFID funded work (Marshall, F et al 2003, Enhancing food chain integrity: quality assurance mechanisms for air pollution impacts on fruit and vegetable systems, Final Technical Report, Project R7530, DFID, UK) that began to examine 1) the nature and important of periurban agriculture to the livelihoods of the poor and to city economies 2) the impact of environmental pollution on the yield, quality and safety of food crops that are important to the poor. It seeks to build new partnerships and new ways of working. The aim is that strategies for investigating and addressing the impacts of pollution on food are planned and instigated in the context of an understanding of the food system as a whole. The livelihoods of the poor are central to this system and channels of communication are opened up with and between the many policy areas and processes that interact with it. Objectives 1. Understanding of seasonal industrial sources and extent of heavy metal contamination in irrigation water, including awareness amongst stakeholders 2. Improved understanding of the relationships between heavy metal levels in irrigation water, accumulation of damaging levels in the edible portion of crops, & implications for cropping methods & farming systems. 3. Improved understanding and greater awareness of source-pollutant-impact relationships amongst stakeholders. 4. Development of / improved awareness of appropriate technical methods of monitoring heavy metal contamination in irrigation water. 5. Improved health monitoring, health statistics, and health awareness amongst health professionals and the public at risk of both consuming contaminated crops / of handling contaminated water during the crop production process. 6. Augment the social, economic, institutional and policy environment for the effective implementation of appropriate measures for monitoring and control. Figure 1: Policy fields related to wastewater irrigation in periurban areas.

3 Key findings Figure 2: Location of study sites at Varanasi 1. Wastewater (both treated and untreated municipal and industrial effluent) contains high level of certain heavy metals. 2. The predominant source of heavy metals are small-scale industrial units operating in the area. A large proportion of these units comprises of unregistered units which operate clandestinely. 3. Soils and crops at the peri-urban areas have high levels of heavy metal contamination. 4. Agricultural sites using wastewater show higher levels of contamination when compared to those using cleaner water. 5. Small farmers growing vegetables with contaminated irrigation water consume these vegetables, thereby raising a serious health concern. 6. Peri-urban areas are an important source of urban vegetable market. Therefore, crop contamination pose a health risk to the urban consumer too. 7. Currently there is neither any quality standard for irrigation water in India nor is there any quality monitoring. 8. Treatment of sewage at treatment plants is not adequate to reduce risk from heavy metal contamination. 9. The standards established by the Prevention of Food Adulteration Act for vegetables and other food crops are much more lenient in comparison to standards established by the European Union and Codex Alimentarius. Summary activities and findings Heavy metals selected The heavy metals sampled include zinc, lead, copper, cadmium, chromium, manganese and nickel. Of these, potentially the most toxic are cadmium and lead. These heavy metals are widely associated with the many small-scale industries in Varanasi that include metal works, paper manufacturers and chemical and paint works. Sampling sites Farmers at The target villages were selected on the basis of the following criteria: 1. There is widespread cultivation of crops that have been identified as particularly important for the livelihoods of the poor. 2. There is a clear source of potentially contaminated water that is being used for irrigation purposes. 3. The villages represent a range of different water use practices which could affect the heavy metal contamination of crops.

4 4. Preliminary meetings suggested that there is good potential to establish effective working relationships with affected communities and other informants in the village. Selection of case studies areas in Varanasi therefore focused on three areas where effluent from industries (associated with heavy metals discharge) could be visibly linked to irrigation use -- (in the vicinity of the city's major sewage treatment works), (to the north east of the city near close to industrial area) and (to the west of the city close to several industrial areas). Summary of results Irrigation by treated or untreated wastewater has increased the heavy metal concentrations in soil and plants of the receiving area. Cadmium concentration in irrigation water was found above the permissible limit set by World Health Organisation (WHO) for irrigation of agricultural land at, and. Heavy metal concentrations in plants show significant spatial and temporal variations.,, and Ni were above the Indian permissible limits, while and Cu were within limits in the edible portion of the crop. Cr concentration was above the permissible limit at site, receiving effluents from Cr-based industries. The results of the present study further suggest that, Cr, and Mn concentrations in plants are influenced by seasonal variations, whereas, Cu,, and Ni did not show any change in uptake pattern due to seasonal variations. The consumption of,, and Ni-contaminated portion of B. vulgaris plants by suburban people of Varanasi may pose health hazards. An important issue is that the contamination levels were frequently higher than permissible limits in the plant tissue, at the same Untreated sewage for irrigation sites as water samples that comply with established safe standards. This has important implications for policy in that programmes aimed at monitoring and controlling heavy metal concentrations in irrigation water sources will not necessarily result in acceptable levels in vegetables. I. Heavy metal concentrations in irrigation water The mean heavy metal concentrations for each of the sample sites are shown in tables 1 and 2. Table 1: Mean levels of heavy metals in irrigation water at, Lota and, Varanasi (August April 2004) Heavy Metal FAO Standard Mean & S.E. (in mg/litre) (mean in mg/litre) Cadmium 0.01 Mean Standard Error Zinc 2.00 Mean Standard Error Chromium 0.10 Mean Standard Error Manganese 0.20 Mean Standard Error Copper 0.20 Mean Standard Error Lead 5.00 Mean Standard Error Nickel 0.20 Mean Standard Error Note: FAO standards have been used due to absence of Indian or EU standards for irrigation water

5 Table 2: Percentage of samples that exceeded FAO standard for HM in water at, and, Varanasi (August April 2004) Site Number of samples Percentage of samples that exceeded standard for Cr Mn Cu Ni (D1) () () (D4) (D5) (L1) (L2) (L3) (L4) (S1) () (S3) Note: Blank cells indicate that no samples exceeded standard II. Heavy metal concentration in soils Whilst none of the samples exceeded the standard for cadmium in 2003, all samples collected in 2004 exceeded the EU standard at. At both and, cadmium concentrations exceeded the EU standard at all sites. Levels of zinc exceeded the EU standard only at one site at. Table 3 summarises the mean (and standard error) heavy metal contamination recorded at each of the sites, whilst table 4 indicates the proportion of the total samples collected that exceeded permissible limits. Table 3: Mean levels of heavy metals in soil at, and, Varanasi (August April 2004) Heavy Metal EU Standard Mean & S.E. Cadmium 3.00 Mean Standard Error Zinc Mean Standard Error Chromium 1.00 Mean Standard Error Manganese No standard Mean Standard Error Copper Mean Standard Error Lead Mean Standard Error Nickel Mean Standard Error

6 Table 4: Percentage of samples that exceeded EU standard for HM in soil at, and, Varanasi (August April 2004) SITE Number of samples Percentage of samples that exceeded standard for Cr Cu () () (D5) (L1) (L2) (L3) (L4) (S1) () (S3) Note: Blank cells indicate that no samples exceeded standard III. Heavy metal contamination of crops Samples of nine vegetables, collected from August 2003 to May 2004, were analysed for heavy metal contamination. Following is the summary of crop contamination levels in Varanasi: Palak: All palak samples from, and were found to be contaminated with lead and cadmium, in exceedence of the European standard. Zinc levels were above the UK standard at, and. Copper levels were found to violate the standards only at. Radish: All radish samples from, and were found to be contaminated with lead and cadmium, in exceedence of the European standard. Zinc levels were above the UK standard at, and. Cauliflower: All radish samples from, and were found to be contaminated with lead and cadmium, in exceedence of the European standard. Zinc levels were above the UK standard at, and. Brinjal: Cadmium and lead levels exceeded the standard at all sites in and. Brinjal was not cultivated at. Cabbage: Cabbage was cultivated only at the sites and at, and exceeded standards for cadmium, zinc and lead. Wheat: Wheat samples at, and were found to exceed standards for cadmium and lead. Amaranthus: Cadmium and lead levels exceeded the standard at all sites of, and. Zinc standards were violated at all sites except one site of. Tomato: Both cadmium and lead levels were found to be higher than the standards at all sites of, and where tomato was cultivated. Okra (Bhindi): Exceedence of standards was detected for cadmium, lead and zinc.

7 Table 5: Percentage of samples that exceeded UK (for zinc and copper) and EU (for cadmium and lead) standards for heavy metals in crops at, and, Varanasi (August April 2004) Site Percentage of samples that exceeded standard for Cu Palak Amaranthus Bhindi Not monitored Brinjal Not monitored Cabbage Not monitored Cauliflower 40 Not monitored Radish Tomato Wheat Tables: Exceedance of EU and UK standards for heavy metals in crops at, and, Varanasi (August April 2004) (multiples of the standard based on the mean value of all samples collected at each site) Table 6: Palak L1 L Cu Table 7: Amaranthus D5 L1 L4 S

8 Table 8: Okra D Table 9: Brinjal Table 10: Cabbage Coloured water in drain Table 11: Cauliflower Cu Table 12: Radish L Table 13. Tomato Treated municipal sewage at Microgramme per gramme Figure 3: Crops irrigated with wastewater show higher levels of contamination (Cadmium in Palak at, Varanasi) Clean water Wastewater EU standard Indian standard D5 L1 Table 14: Wheat D5 L1 L4 Note: UK standards have been used for Zinc and Copper. For all other heavy metals EU standards (which are often more stringent than Indian standards) have been used as the benchmark. IV. Summary of experiment to determine the link between contaminated irrigation water and contamination of crops. An experiment was conducted to determine the contribution of wastewater irrigation to heavy metal contamination in crops at two sites in Varanasi ( and ) between September and December This experiment also enabled us to assess the value (in terms of a reduction in HM contamination in crops) of making a switch to clean water irrigation at sites where wastewater had been used for some time. This experimental study clearly indicates that crops irrigated with wastewater are more highly contami-

9 nated with heavy metals than those irrigated with clean water (based on basic t-test comparisons at this stage). This suggests that the current irrigation practices can influence the safety of food at the study sites, and that contamination is not entirely determined by accumulated heavy metals in the soil. The phyto-available heavy metal concentration in soils after harvest was significantly lower than at the time of planting, indicating crop uptake which exceeded additions to the soil during the growing period. It was also very interesting to note that the phyto-availability of heavy metals in soils at the wastewater irrigated sites was significantly higher than at the clean water sites. Table 15: Mean levels of heavy metals in plants (non-washed) at and Heavy metal Type of water used for irrigation Site Site Site D6 Site L4 Site L5 Cadmium Clean water Wastewater Zinc Clean water Wastewater Chromium Clean water Wastewater Manganese Clean water Wastewater Copper Clean water Wastewater Lead Clean water Wastewater Nickel Clean water Wastewater Note: Figures within brackets denote standard error In washed plants, cadmium and lead exceeded standards at all the sites. Zinc was found to exceed the standards at all sites of and using wastewater and at two sites ( and L4) using clean water. Copper levels exceeded the standard at all sites of and using wastewater (table 33). It was found that difference in the levels of heavy metals between washed and non-washed plants is not significant. V. Assessment of heavy metal contamination in the food basket of the peri-urban poor at, Varanasi The number of crops analysed for heavy metal contamination were increased to include all crops grown in in order to ascertain the exposure of the peri-urban poor to heavy metals through their diet. Heavy metal contamination was measured in 14 food crops. The results of this study was in line with earlier findings with cadmium and lead exceeding the EU permissible limit for all crops, while certain other crops were found to have high concentration of zinc. VI. Impact of soil amendment practices on concentration of heavy metals in soils and crops A field experiment was conducted from end of October to December 2005 at site of for assessing the impact of soil amendments on heavy metals uptake and bioaccumulation in edible portion of Palak grown at site having long term uses of treated sewage water for irrigation. Soil samples were subjected to five treatments - irrigation with clean water, irrigation with wastewater, treatment with NPK, treatment with farmyard manure and treatment with FYM+N. Results show that amongst all fertilizer options, use of farmyard manure is associated with the lowest heavy metal concentration in

10 phytoavailable soil and in Palak. VII. Food basket survey at, Varanasi A survey was conducted at to ascertain the pattern food consumption, to assess the extent of wastewater use in irrigation, pattern of irrigation and the main source of food consumed by the peri-urban poor. It was found that due to flood irrigation by wastewater the underground water table has risen by ft, but has been rendered unfit for human consumption due to consumption. The survey confirmed earlier findings from other areas that small and poor farmers primarily consume the vegetables they grow, often with the help of wastewater irrigation. PROJECT TEAM Dr Fiona Marshall (Project Leader) Deputy Director SPRU (Science and Technology Policy Research) The Freeman Centre, University of Sussex, Brighton, BN1 9QE F.Marshall@sussex.ac.uk Tel: +44 (0) Ravi Agarwal Director, Toxics Link, New Delhi H2 (Ground Floor), Jungpura Extension New Delhi ravig1@toxicslink.org Tel: +91-(0) , Dr Madhoolika Agrawal Department of Botany, Banaras Hindu University, Varanasi, Uttar Pradesh madhoo@bhu.ac.in Tel: +91-(0) Chandrachur Ghose Research Officer SPRU (Science and Technology Policy Research) The Freeman Centre, University of Sussex, Brighton, BN1 9QE C.Ghose@sussex.ac.uk Dr Darshan Singh Bhupal Agricultural Economics Research Centre, University of Delhi Delhi dsbhupal@yahoo.com Tel: +91-(0) , Satish Sinha Toxics Link, New Delhi H2 (Ground Floor), Jungpura Extension New Delhi satish@toxicslink.org Tel: +91-(0) , Dr Abhay Kumar, Project Coordinator Toxics Link, New Delhi H2 (Ground Floor), Jungpura Extension New Delhi abhay@toxicslink.org Tel: +91-(0) , Rajesh Kumar Sharma, Doctoral candidate Rajeev Pratap Singh, Doctoral candidate Supriya Tiwari, Doctoral candidate Department of Botany, Banaras Hindu University, Varanasi, Uttar Pradesh 225 Tel: +91-(0) More information on the project website: The project is funded by the UK Department for International Development (EngKar R8160)