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Toxic Tours - XIV: Our Stolen Future: The effects of pesticide contamination on future generations

By Meena Menon

Studies by naturalists and scientists reveal that pesticide contamination has unalterably affected the breeding biology of birds such as raptors and sarus cranes. The contamination, most likely, has been passed on through the birds' prey base

Sterile bald eagles in Florida, vanishing otters in England, reproductive failures among minks near the Great Lakes in the USA, deformed herring gulls at Lake Ontario. Since the 1950s, observations by keen naturalists and scientists have tried to understand sudden unexplained changes in wildlife and human reproductive patterns.

In their book Our Stolen Future, Theo Colborn, Dianne Dumanoski and John Peterson Myers document scientific research on the disruptive havoc created by man-made chemicals on the hormone system. The issue of endocrine disruption was brought into the open and evoked tremendous response in terms of policy and research. As early as the 1950s, researchers reported that man-made chemicals like DDT could derail the sexual development of roosters and, through what appeared to be hormonal action, lead to chemical castration (Our Stolen Future).

Pesticides can have a wide-ranging impact on humans, flora, fauna and their environment. However, closer home, despite the gravity of the problem in India, the lack of a proper policy and an even bigger lack of political will hamper stringent control on the future use of pesticides and their manufacture.

A report, The Impact of Toxics on Biodiversity in India, by the Chintan Environmental Research and Action Group, New Delhi, for the National Biodiversity and Action Plan (NBSAP), states: “Firstly, coast-to-coast, the country is being discovered to be pitted with toxic hot-spots. Endosulfan in Kerala, pesticide poisoning of peacocks in Morena, Madhya Pradesh, and sarus cranes in Bharatpur, Rajasthan (poisoned as they enter fields as crop-raiders), mass mercury pollution by Hindustan Lever’s operations in Kodaikanal, toxic PVC plastic recycling across the country, incineration and open burning of waste and chlorinated compounds everywhere in India, backyard lead recycling, poorly dumped waste that seeps in to poison the groundwater: these and more are a part of India’s toxic present.”

“And then, policy is mostly playing quack. There has been no attempt to reduce and phase out, on priority, toxics from the production and consumption cycle, nor any concrete tangible action seen to protect people from such exposure.”

Chintan’s report goes on to say that out of 47 case studies it found on toxics and biodiversity, only (7) 15% are field studies. The rest -- 85% (40) -- are laboratory studies. Of the 12 studies on the impact of toxicity on mammals, most are mainly on rats and are laboratory studies. Seven studies are on crabs. Hence, the total number of studies on aquatic organisms is 29, which is more than 60% of the total collected case studies in its literature survey. Thus, there is poor representation of natural biodiversity in the range of species studied for the impact of toxic substances.

There are no studies done on either large mammals or endangered species. The latter, being at the top of the food chain, could be the repository for a variety of pollutants that could be impacting them in ways not yet understood due to lack of available data, the report adds.

About 40% of the pesticides used in India are organochlorines, which include banned substances like DDT, aldrin, endosulfan, lindane, chlordane and dieldrin.

Rishad Naoroji of the Bombay Natural History Society (BHNS) undertook a study on the breeding biology of resident raptors in Corbett National Park, Uttar Pradesh, during 1990-1993. The park is home to the Himayalan greyheaded fishing eagle. Naoroji’s study reported that the greyheaded fishing eagle bred unsuccessfully. Eggs from seven nests monitored during this period did not hatch; three nests hatched but the young were either found dead in their nests or disappeared within a week of hatching. Eggshell fragments, which were collected from one nest in April 1991, were deformed.

Analysis of the thinner-than-normal eggshells in the US by Dr Robert Risebrough of the Bodega Bay Institute, California, revealed a number of organochlorine compounds. The relatively high amounts of DDT and its metabolites indicated recent DDT applications in local or nearby areas. The evident thinning of the shells was most likely an effect of DDE, usually the principal metabolite of DDT in the environment, and the compound considered primarily responsible for shell-thinning (Journal Bombay Natural History Society, Vol 94(1997)).

PCB congeners and dieldrin were also detected, but at relatively low levels. However dieldrin, which is highly toxic to birds of prey, has been implicated in the population decline of raptors in Europe and North America. Locally it is most likely derived from aldrin, which has been used widely in north India. These contaminants could have been passed on only through the prey base, which, for this species, is solely fish.

The presence of the contaminants in the local riverine food web is therefore a plausible cause of at least some of the unsuccessful breeding attempts at the Corbett National Park (ibid).

The study notes that the higher reaches of the Ramganga river, which flows through most of the park, are intensely cultivated and pesticides used on a large scale. The contaminants probably run off into the water system during the heavy monsoons. The study concludes that the species is most likely seriously threatened in Corbett and likely to be similarly affected throughout its range in India. And so our unthinking and extensive use of toxic chemicals has threatened “this mainly sedentary species which is fully dependent on the Himalayan riverine system”.

Another study on the Indian sarus crane in Gujarat, by H S Singh and Ketan Tatu (1997-1999) and the Gujarat Ecological Education Research (GEER) Foundation, found the sarus crane in danger of pesticide toxicity. Excreta samples of the birds contained high concentrations of BHC and aldrin. Aldrin has already proved dangerous to sarus cranes in Keoladeo National Park, Bharatpur, in Rajasthan. Between 1988 and 1990, the national park lost 18 cranes. The birds exhibited unusual nodding and bobbing, side-to-side movements, violent wing-beating, intermittent jumping, unsuccessful attempts at taking off and collapsing on the ground -- all of which are recognised symptoms of aldrin poisoning (Murlidharan S, 1996, Poisoning the Sarus 1992(1): 2-7).

M S Saini and V R Parshad of the Punjab Agricultural University observed that migratory birds carry pesticide residues to other ecosystems and poison their predators and/or cause reproductive failures, thus revealing the global impact of pesticide contamination.

The annual report for the project on the effect of environmental contamination on raptors, with special reference to Shaheen (Dr Vibhu Prakash BNHS, 2002), claimed that analysed tissue samples of raptors in the Keoladeo National Park, Bharatpur, in Rajasthan, did not indicate a high level of bio-accumulation of pesticides, which could cause breeding failures. The report said the causes of the raptors’ decline in the park could be a combination of various factors, including disease.

The white-backed vulture has showed a drastic decline in nesting populations, and 100% breeding failure. It showed symptoms of pesticide poisoning, such as non-hatching, breaking of eggs in the nest, failure to lay eggs and the death of nestlings. Breeding failures in the park have been reported in studies since 1988, and a survey of pesticide use around the park revealed extensive use of aldrin, dieldrin, endosulfan, heptachlor and DDT. High adult mortality is also recorded. However, vulture tissue samples from the park did not show any significant pesticide load. Breeding failure could be due to organochlorine contamination in the tissue, but the cause of adult mortality was not clear, the report said.

The results of the analysis on the tissue of vultures and their eggs revealed traces of DDT metabolites, dieldrin in the pectoral muscle, yolk cells and muscles. Samples of fish have also been collected regularly from the park, since 1988, as fish constitutes the raptors’ major food. But the analysis has so far been clean.

Still, the fact that India’s soil and water are contaminated with pesticides is beyond doubt. Studies only serve to pinpoint the extent of the damage. The habitats of birds and other wildlife species are already under threat -- their protected status does not make them immune to the dangers of pesticide contamination. While humans and animals face the ongoing lethal impact of pesticides, which could include endocrine disruption and cancer, the chilling thought is that future generations are not exempt either.

-- InfoChange News & Features, October 2003