India is one of the major consumers of organochlorine pesticides, for agriculture and public health programs and also a generics giant as it is one of the few remaining countries still engaged in the large scale manufacture, use and export of some of the toxic chlorinated pesticides. Although these chemicals were banned for agricultural practices in the late 1990s, substantial amounts are still being used for the eradication of vector borne diseases such as malaria and filaria. Apart from this, as a result of its fast industrial and urban development, the use of the some other chemicals, especially polychlorinated biphenyls (PCBs) is on the increase. As the pioneering workers in this aspect in India, we have been observing the spatial and temporal trends of contamination by the chemicals such as dichlorodiphenyltrichloroethane (DDT), hexachlorocyclohexanes (HCHs), chlordanes (CHLs), hexachlorocyclohexane (HCB) and PCBs in the environmental and biotic samples including human matrices for the past two decades and more.  We found all these chemicals ubiquitously in air, water, soil and sediment, wildlife including mussels, fish, birds and in marine and river dolphins and in different food stuff. Especially the finding of persistent organochlorine residues in human breast milk of India (Tanabe et al., 1990; Tanabe and Kunisue, 2007; Subramanian et al., 2007; Devanathan et al., 2009) is of particular concern because the infants and children may be more susceptible to the toxic implications of toxicants than adults.

Starting from our earlier studies (Tanabe et al., 1990) to the most recent one (Devanathan et al., 2009) we noticed the occurrence of these chemicals in human breast milk collected from mothers living in and near various locations such as agricultural and fishing villages, small towns, metropolitan cities, municipal dumpsites, etc. Our results showed very much interesting spatial and temporal variations in the samples collected in the years 1988, 2002 and 2008. In the samples collected during 2002-2003 we (Subramanian et al., 2007) found that all the samples from Chennai (metropolitan city; 12), Perungudi (municipal dumpsite in the outskirts of Chennai city; 20), Parangipettai (fishing village; 6) and Chidambaram (agricultural town; 8) contained measurable quantities of all the five organochlorines (HCHs, DDTs, CHLs, HCB and PCBs) (Fig. 1). It could be seen from the figure that PCBs in the samples from all the locations are more or less the same except some outliers in Perungudi and somewhat lower values in the temple town Chidambaram. DDTs in Chennai mothers were few times higher than those from Perungudi, Parangipettai and Chidambaram which can be explained by the possible use of DDT for vector control within city limits. Ironically, Chennai, which do not have any agricultural activity, had one order higher HCHs, the chemical which is used predominantly for agricultural purposes, than at places like Chidambaram and Parangipettai, places which are abound with agricultural activities. Whether HCHs are still in use by the local government inside the city limits for insect control or by the private entrepreneurs and public inside their premises is to be known.

Fig. 1. Concentrations of organochlorines (ng/g lipid wt.) in human breast milk from Tamil Nadu State, India. Values in parentheses are mean concentrations. Error bars show ranges. (a) values significantly higher than in other three regions p<0.01. (b) Significantly higher than in Chidambaram p<0.01 (c) Significantly higher than in Parangipettai and Chidambaram p<0.01. (Subramanian et al., 2007).

Further, it could be seen from Figure 2 that there is a clear temporal increase in the levels of HCHs and DDTs in the samples collected from Chennai during 2002-2003 mothers (Subramanian et al., 2007) when compared with the results published by Tanabe et al. (1990) from the samples collected during 1988, revealing that Chennai mothers are exposed to higher amounts of HCHs and DDTs all through these years than the people living in other parts of the state. Levels of both the chemicals drastically decreased in the breast milk samples from Parangipettai and Chidambaram indicating the effective implication of the bans imposed by the Government of India whereas the exemptions permitted for the use of these compounds for vector control are in use in Chennai and possibly in other metro cities of India.

Comparison of some of our data with the same pollutants in mothers’ milk from some other Asian countries (Tanabe and Kunisue, 2007) showed that Indian levels of DDTs and PCBs were lower than some Asian countries and comparable to some others, whereas HCHs were higher than almost all the countries except in a location in China (Fig. 3), indicating a prominence in HCHs contamination in India.

Fig. 2. Temporal changes of HCHs and DDTs in human milk from Chennai city, Parangipettai and Chidambaram, India. Data for the year 1988 were cited from Tanabe et al. (1990). Values in parentheses are mean concentrations. Error bars show ranges in concentrations. Levels in 1988 were significantly higher than in 2002 p<0.01 (Subramanian et al., 2007).

Concentration (ng/g lipid wt.)

Concentration (ng/g lipid wt.)

Fig. 3. Concentrations of DDTs and HCHs in human breast milk from general public in Asian countries (Tanabe and Kunisue, 2007).

While our previous studies showed differences in the organochlorine levels in locations within a state (Tanabe et al., 1990; Subramanian et al., 2007), our recent work (Devanathan et al., 2009) on the metropolitan cities of India (Mumbai, Kolkata, New Delhi and Chennai) revealed nationwide differences (Fig. 4). For example, while Mumbai mothers had significantly lower mean levels of DDTs (450 ng/g fat wt.) than New Delhi (1500), Kolkata (1100) and Chennai (1200) in their milk, Chennai mothers had higher HCHs (4500 ng/g fat wt.) than the mothers from New Delhi (1800), Mumbai (220) and Kolkata (670). PCBs levels were comparable among all the four cities (New Delhi-23ng/g fat wt; Mumbai-30; Kolkata - 40; Chennai-34). Of the four metropolis evaluated, Mumbai seems to be less contaminated (DDTs-450 ng/g; HCHs-220 ng/g) with respect to these two contaminants, than the other three cities.

Fig. 4. Nationwide distribution of organochlorine pollutants in India (Devanathan et al., 2009)

The values reported by Tanabe et al. (1990) in the samples collected during August to December 1988 were higher than the levels observed by us recently in several places in India in the samples collected during 2002-03 and 2008 (Subramanian et al., 2007; Devanathan et al., 2009) (except in the case of Chennai), revealing the effectiveness of various bans and restrictions imposed in recent years by the Government of India on the usage of these compounds. Further, our studies also revealed that there is region specific usage of the two chemicals, DDTs and HCHs in the cities in the east, west, north and south of India.

The levels of other two compounds analyzed by us (CHLs and HCB) were one to three orders lower than PCBs, DDTs and HCHs and thus not of much environmental importance in India, at least at present. These two compounds did not reveal any clear spatial or temporal variation.

Our results show that the regulations imposed by the Government of India on the usage of organochlorines, especially DDT and HCHs have impact on the levels in Indian environment and biota including human. Even beyond the decrease in the past decade, the levels of these compounds are still higher in particular locations, especially in metropolitan cities, indicating still continuing usage, either by the government for disease control or by public in their premises for insect control. A strict imposition of environmental regulation and management of these chemicals in India is necessary.

References

Devanathan, G., Subramanian, A., Someya, M., Sudaryanto, A., Kunisue, T., Takahashi, S., Chakraborty, P. and Tanabe S. (2009) Persistent organochlorines in human breast milk from major metropolitan cities in India. Environ. Pollut. 157, 148 – 154.

Subramanian, A., Ohtake, M., Kunisue, T. and Tanabe, S. (2007) Higher levels of organochlorines in mothers’ milk from Chennai (Madras) city, India. Chemosphere. 68, 928 - 939.

Tanabe, S., Gondaira, F., Subramanian, A., Ramesh, A., Mohan, D., Kumaran, P. L.,  Tasukawa, R. and Venugopalan, V. K. (1990)  Specific pattern of persistent organochlorine residues in human breast milk from South India.  J. Argic. Food Chem. 38,  899-903.

Tanabe, S. and Kunisue, T. (2007) Persistent organic pollutants in human breast milk from Asian developing countries. Environ. Pollut. 146, 400 - 413.

ENVIS CENTRE Newsletter Vol.7,Issue 3 July 2009