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Title: Risk assessment of endocrine disrupting pesticides in biological systems
Author: McKinlay, Rebecca
ISNI:       0000 0004 2682 5799
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2009
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Endocrine Disrupting Chemicals (EDCs) are a diverse array of natural and manmade substances capable of interfering with hormonally mediated processes. They are particularly harmful to cells that are differentiating and dividing rapidly, can stimulate unwanted cell growth, and can interfere with normal epigenetic imprinting causing changes that in some instances are heritable. Due to their epigenetic effects and effects on tissue growth and development, organisms at certain life stages are more vulnerable than others and effects may manifest a long time after exposure. The risks posed to human and environmental health by these compounds are currently unknown, but there is a growing scientific consensus that precautionary measures and further research to understand and quantify these risks are needed. Endocrine Disrupting pesticides represent a subset of EDC capable of reaching humans from a diverse range of sources via many different exposure routes. No definitive lists or screening methodologies exist to identify them. In the UK, exposure routes involving occupational pesticide use for agricultural purposes or the residues of these pesticides in food and water are well quantified but other sources of exposure are not. If risk management measures are to be enacted to protect the population, these exposures will have to be quantified and the risks they pose assessed. This project aims to identify the hazards posed by ED pesticides to humans living in the UK, prepare a framework for the assessment and management of risks they pose, identify the tasks that remain to be completed before such a framework could be implemented, and to investigate poorly documented ED pesticide exposure sources. Current toxicological testing of pesticides was found to be inadequate. Properties frequently exhibited by EDCs, such as non-monotonic (j-type) dose responses and the additive and synergistic actions of compounds were not taken into account. Only active ingredients are legally required to be tested even although adjuvants used to improve formulation effectiveness are not always inert and formulations can be more toxic or have greater ED potential than their active ingredients alone. Adjuvants are assessed on a reactive basis, which is not adequate to protect public health. A tiered risk assessment and management framework capable of screening potential ED pesticides and making recommendations for risk management can be created using existing deterministic and probabilistic models of human pesticide exposure. The identification of critical groups that are more vulnerable than the general population to the effects of EDCs allows risk assessment and management to be tailored to protect these groups, allowing the risk to both these groups and the general population to be minimised, in keeping with the precautionary principle. Further work is required, however, to collect appropriate datasets to model non agricultural exposure routes and model the exposure of rural residents and bystanders. Assumptions made in the creation of foreign models would need to be checked to ensure they were compatible with UK conditions. Appropriate ADIs for EDCs showing non-monotonic dose responses would also need to be determined, and exposure profile differences between people living in urban, periurban and rural environments would also have to be taken into account. A number of ED pesticides used for medicinal, veterinary and domestic purposes and the municipal and commercial maintenance of infrastructure and recreational areas were identified. Unfortunately little could be determined about the factors influencing their use by the public. The number of years spent in secondary education correlated positively with non ED medicinal pesticide use and both ED and non ED veterinary and domestic use. It was unclear why this should be. Golf courses were the most heavily treated publicly accessible areas studied and used the most ED pesticides. Large parks received least, with pesticide use concentrated on hard surfaces and high maintenance ornamental areas. Pesticide use in parks is dominated by herbicides. Applications to pavements and other publicly accessible hard surfaces consisted almost entirely of glyphosate based herbicides. Herbicide applications on pavements and in parks mostly take place in the spring and early summer. The bulk of pesticide applications on golf courses were applied in the autumn. Contractors carrying out maintenance work for local authorities were found to use more pesticides than local authority employees. Non chemical methods of ectoparasite, pest and weed prevention and control have the potential to reduce pesticide use. Some of the methods currently in use, however, were found to be more costly and challenging to implement than chemical methods. The integration of these into parasite, pest and weed prevention and control strategies where possible and their further should be encouraged.
Supervisor: Voulvoulis, Nick Sponsor: Holly Hill Trust
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral