Mahmood A. Khwaja
Khwaja@sdpi.org
Like other chemicals of the persistent organic pollutant (POP) group, the pesticide DDT (dichlorodiphenyltrichloroethane), is also persistent in nature and does not degrade in the environment through biological, physical or chemical processes. Being non-degradable, DDT can travel long distances and can accumulate in animal and human bodies due to its solubility in fats. Humans and wildlife can come in contact with DDT through contaminated air, water, soil and food. Even in extremely small amounts DDT can injure human health and the health of other organisms. It is harmful to the stomach, intestines, liver and kidneys, and can affect nervous system and cause reproductive development defects and cancers and tumors. Women, children and infants are especially vulnerable to certain effects of DDT.
In 2005–6, Sustainable Development Policy Institute (SDPI) and the Institute of Chemical Sciences (ICS), Peshawar University, in collaboration with the NWFP Environmental Protection Agency and with support from IPEP (International POPs Elimination Project), South Asia, carried out a study to examine the adverse environmental and health impacts of residual DDT in and around a DDT manufacturing factory, Amman Gharh, Nowshera, NWFP. During the site survey and field-visits a few composite samples of soil (4), sediments (4), water (9) and from within the factory (7) were collected in and around the factory area and chemically analyzed. The residual DDT levels in the soil samples were found to be alarmingly higher than the DDT standard minimum risk limit (MRL) for soil, despite the closure of the factory several years ago.
In view of DDT’s known toxicity, accumulative characteristics and adverse environmental and health impacts, its persistence in and around the DDT factory in Amman Gharh may cause most serious consequences for ecosystem function, food safety and other aspects of human health. There is a dire need to carry out an extensive survey of the Amman Gharh area to examine DDT levels in different segments of its environment and to assess the likely impacts of DDT exposure on the general public, especially health of infants, children, women and other vulnerable groups.
For the present study, eighty-one (81) soil samples were collected within a half Km of the old gate of the factory in eight directions. These directions, as indicated by the field-compass from the rubble of construction material, were north (N), north-west (NW), west (W), south-west (SW), south (S), south-east (SE), east (E) and north-east (NE). Soil samples were collected on clear dry days during three field-visits undertaken on December 2nd (26 samples) and December 16th (25 samples) 2006 and January 11th 2007 (30 samples). Soil samples were also collected from the soil surface, at 0.15, 0.30, 0.45 & 0.60 meter depths from a single sampling point in each of the six directions.
Analytical data indicated that 90.91% of the soil samples were contaminated with DDT, with 66.6% of the samples indicating residual DDT levels higher than the DDT minimum risk level in soil (0.05 ug/g). Only soil samples examined in the North East indicated residual DDT levels (average 0.02 +/- 0.01) below the minimum risk level (MRL) of 0.05 ug/g. Soil samples collected between 325 and 520 meters in the North and North West directions also indicated residual DDT levels below MRL (between 0.01 and 0.04ug/g.) The highest residual DDT level (11.30 ug/g) was found 65 meters NW of the old factory gate. However, soil in the SE direction appeared to be most contaminated (average 6.70 +/- 1.25 ug/g), showing 5.19 ug/g residual DDT in soil sample collected as far away as 520 meters from the old factory gate. Soil in the South also appeared highly contaminated, with an average DDT residual level of 7.16 +/- 1.70 ug/g from 65 – 390 meters from the factory. In all directions except NE around the factory area, residual DDT levels in soil samples generally showed a decrease with increasing distance from the factory.
Soil samples at 0.15 – 0.30meter depth from N and NE directions were found to be below minimum risk level (MRL), so further depth-studies of soil in these two directions were not conducted. For soil between the surface and 0.60 meters deep, the highest residual DDT level (5.78 +/- 3.94 ug/g) was observed in samples from the NW, followed by samples from the West (4.88 +/- 3.80 ug/g). The lowest residual DDT level (0.71 +/- 0.95 ug/g) was observed for soil samples in the SW. Except for the NW and W directions, soil samples did not show residual DDT beyond a depth of 0.45 meters. However, even at the 0.60 meter depth in the West direction, compared to MRL (0.05 ug/g) for soil, alarmingly high level (0.58 ug/g) of residual DDT was observed. A comparison of average residual DDT levels at different depths indicated a generally decreasing trend in residual DDT from 6.28 +/- 3.90 to 0.10 +/- 0.22, with increasing depth from surface to 0.60meter of the soil around the demolished DDT factory area.
It is evident from the above data that a very large area of the soil around the demolished factory is highly contaminated with DDT, despite the closure of the factory several years ago. During the field-visits, highly contaminated sites in the South, South West and South East were observed to be mostly residential areas, with houses less than 200 meters from the old factory gate. We also observed that the demolished factory compound had already become a play ground for children and grazing/feeding place for stray cattle and free-range chickens.
The toxicity, persistency, accumulative nature, transportation and adverse environmental and health impacts of DDT, even in extremely small amounts, are well established. DDT contamination in and around the demolished DDT factory areas in Amman Gharh may cause most serious consequences for ecosystem function, food safety and other aspects of human health, especially the health of children.
We strongly recommend that the factory area be immediately declared a dangerous area. Standard “Danger” signs with inscriptions in local languages should be installed all around and the area should be banned for human activities. A fence/wall may also be constructed, at the earliest, around the factory area, to prevent entrance of children, animals, cattle, and chickens.
Exposure to DDT is known to be increased by a lack of vegetation in the affected soil: therefore, steps should be taken to plant vegetation in the area, so as to minimize the risk of continued soil toxicity.
Advocacy campaigns and awareness-raising activities should be carried out as soon as possible for the residents in the immediate surroundings of the factory area, especially for children and teachers in the schools of Amman Gargh.
Further samples should be taken from the West, South West and South directions, and samples must be taken at greater depths, as earlier sampling found unacceptable levels of DDT at locations 550 meters from the factory gate and 0.6 meters deep.
In order to evaluate the risk associated with the DDT-contaminated site, studies using bio-indicators like eggs, adipose tissue, milk, fish, birds, endocrine disruption and cholinesterase levels should be initiated in these areas. Earlier reports have indicated high DDT levels in the eggs sampled near Peshawar, NWFP.
The presence of high level of DDT in the soil samples indicates the persistence of DDT in this high temperature zone of Pakistan, though there were earlier reports that DDT may not be persistent in this part of the world. The present study necessitates a fresh look into those findings.
There is also a dire need to identify other DDT (and other POPs ‘hot spots’) in the country and to investigate the exposure levels and resulting health threats to local populations in areas where the formulation, storage and application of DDT had been conducted.
Further work is also needed to see if other toxic degradation products like DDE are present in the vicinity of the demolished DDT factory.
This study has indicated the most alarming situation of DDT residues in soil samples. There is a need to look into the feasibility of employing the reported processes for decontamination of DDT from the soil in and around the factory area. Pakistan’s National Implementation Plan (NIP), obligatory under Article 7 of the Stockholm Convention, elaborates the current situation on POPs, including DDT, and states the commitment and actions that the Government intends to undertake in the management and control of POPs for the next 15 years starting from 2007. Among the challenges in the management of POPs, NIP identifies the lack of facilities for safe disposal of wastes (consisting of, containing or contaminated with POPs) and the very limited and financial and technical resources for remediation of the contaminated sites. Details of activities for rational management of POPs pesticides, including obsolete stocks and contaminated sites by 2010 are also contained in the NIP document.
Pakistan needs to ratify Stockholm Convention as soon as possible, so that with the in-coming financial and technical support from the developed countries, as agreed in Articles 12 (3) & 13 (2) of the Convention, the activities outlined in NIP may be started.
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