Exposure science
Exposure science is the study of the contact between humans and harmful agents within their environment – whether it be chemical, physical, biological, behavioural or mental stressors – with the aim of identifying the causes and preventions of the adverse health effects they result in. This can include exposure within the home, workplace, outdoors or any other environment an individual may encounter. The term 'exposure' is the umbrella term for many different types, ranging from ultraviolet exposure, exposure to the chemicals in the food we eat, to exposure to long working hours being the occupational factor most attributable to the burden of disease.
The need for the field arises from the expansive range of exposures which have resulted in negative health outcomes for humans and other organisms, and mainly focus on the relationship between external exposure, internal exposure and dose. By tightly integrating the fields of epidemiology, toxicology, biochemistry, environmental science and risk assessment, holistic comprehension of an exposure is achieved to protect human and ecosystem health on an individual, community and global levels. Though the history of exposure science had an initial slow start, developments have significantly accelerated in the past three decades, including the beginnings of the formation of the "exposome". However, there is still much unknown and research in the field is only expanding to cover the increasing amount of identified exposures.
Need
The essentiality of exposure science research extends from the wide range of adverse health outcomes which burden the population. The World Health Organisation predicts that approximately 24% to 40% of the global disease burden is the result of environmental factors, representing the major health burden in developed countries, and indoor smoke from cooking fuels causes 3.8 million deaths every year. Other morbidities and mortalities as a result of exposure also include cancers, autism, Parkinson's, and cell damage which causes diabetes, cardiovascular diseases and lung diseases.Since research began, there has been many breakthroughs which have improved and protected the health of individuals. An example is the link between UV exposure to the development of all three major forms of skin cancer, which ultimately led to the development of preventions like sunscreen awareness. Exposure to prenatal infections has been linked increased risks of autism and schizophrenia. The development of clothing and materials which protect health care workers from infection exposure, and firefighters from heat exposure, has led to increased protection within these occupations.
However, it is not only human health that exposure science aims to understand and protect, and there are many documented cases where exposure to human activity harms the environment. In 2003, it was discovered that liver damage in fish in Puget Sound was linked to water contamination with polycyclic aromatic hydrocarbons found in coal and gasoline. Majorly, there has also been the discovery of the depletion of the ozone layer as a result of chlorofluorocarbons and halons found in refrigerators, air conditioners, aircraft halons and aerosol cans. The production of greenhouse gases from sources such as transport and agriculture has been strongly linked to global warming, which is subsequently causing rising sea-levels and damage to the environments in which many species live within.
History
One of the earliest accounts of exposure research was conducted by Hippocrates in 400 BC, when he published 'Air, Water, and Places' describing that air, water, food and living quality influenced the prevalence of human disease. Following well into the late 1900s, there became more and more studies published, such as the link between water contamination and cholera in London in 1855. However, one of the note worth publications which laid the foundations for the expansion of exposure science into what it has become today was the 'Human Exposure Assessments for Airborne Pollutants: Advances and Opportunities' by the National Research Council. It was the first to "define the core principals of exposure assessment", and has resulted in increased investments in exposome technologies, growing exposure science programs like HELIX and the National Exposure Research Laboratory. The most recent development in exposure science is the shifted focus onto the development of an 'exposome' to match the already underway construction of the complete 'genome'.The 'exposome' concept
The concept of the exposome was first defined by Christopher Paul Wild as the "life-course environmental exposures, from the prenatal period onwards." However, similar definitions have been modified from this, including Miller and Jones, who redefined the exposome as "the cumulative measure of environmental influences and associated biological responses throughout the lifespan, including exposures from the environment, diet, behaviour, and endogenous processes." The study of the exposome has now been termed 'exposomics' in reference to all the technologies used to study the environment, cells and chemicals of an organism.The idea stemmed from the pre-existing concept of the 'genome', the complete set of genetically encoded instructions which function the body, of which Wild focussed on throughout his career in exposure assessment and cancer genomics. Understanding the genome has led to the ability to predict those who are predisposed to certain chronic diseases. In his research field, Christopher Wild identifies environmental exposure as the core influencer and mystery of cancer incidence. He concluded the need for the 'exposome', like the genome, to map the complete set of environmental exposures a human encounters throughout the course of their lifetime in order to easily prevent and identify sources of exposure-caused chronic diseases, along with target age groups.
In 2012, Wild continued to extend his description of the exposome and its entailments. He includes internal bodily processes such as metabolism, hormones, microflora and oxidative stress, external exposures such as radiation, infectious agents and diet, and additionally social, economic and psychological exposures. Increased ease of genotyping and studying polymorphisms saw a major shift to gene-disease related studies in the 1990s and more recently new study designs allow researchers to follow increasing sample sizes. However, also in 2012, Wild went on to describe the realistic tools and methods one could use to effectively develop the exposome. This included biomarker omics, sensor technologies and imaging.