Environmental epidemiology is a branch of
epidemiology
Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in a defined population.
It is a cornerstone of public health, and shapes policy decisions and evide ...
concerned with determining how environmental exposures impact human health. This field seeks to understand how various external risk factors may predispose to or protect against disease, illness, injury, developmental abnormalities, or death. These factors may be naturally occurring or may be introduced into environments where people live, work, and play.
Scope
The
World Health Organization
The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of ...
European Centre for Environment and Health (WHO-ECEH) claims that 1.4 million deaths per year in Europe alone are due to avoidable environmental exposures. Environmental exposures can be broadly categorized into those that are proximate (e.g., directly leading to a health condition), including chemicals, physical agents, and
microbiological
Microbiology () is the scientific study of microorganisms, those being unicellular (single cell), multicellular (cell colony), or acellular (lacking cells). Microbiology encompasses numerous sub-disciplines including virology, bacteriology, pro ...
pathogens
In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a ger ...
, and those that are
distal (e.g., indirectly leading to a health condition), such as socioeconomic conditions,
climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
, and other broad-scale
environmental change Environmental change is a change or disturbance of the environment most often caused by human influences and natural ecological processes. Environmental changes include various factors, such as natural disasters, human interferences, or animal in ...
s. Proximate exposures occur through air, food, water, and skin contact. Distal exposures cause adverse health conditions directly by altering proximate exposures, and indirectly through changes in ecosystems and other support systems for human health.
Environmental epidemiology research can inform government policy change, risk management activities, and development of environmental standards.
Vulnerability
Vulnerability refers to "the quality or state of being exposed to the possibility of being attacked or harmed, either physically or emotionally."
A window of vulnerability (WOV) is a time frame within which defensive measures are diminished, com ...
is the summation of all risk and protective factors that ultimately determine whether an individual or subpopulation experiences adverse health outcomes when an exposure to an environmental agent occurs. Sensitivity is an individual’s or subpopulation’s increased responsiveness, primarily for biological reasons, to that exposure. Biological sensitivity may be related to developmental stage,
pre-existing medical conditions, acquired factors, and
genetic factors. Socioeconomic factors also play a critical role in altering vulnerability and sensitivity to environmentally mediated factors by increasing the likelihood of exposure to harmful agents, interacting with biological factors that mediate risk, and/or leading to differences in the ability to prepare for or cope with exposures or early phases of illness. Populations living in certain regions may be at increased risk due to location and the environmental characteristics of a region.
History
Acknowledgement that the environment impacts human health can be found as far back as 460 B.C. in
Hippocrates
Hippocrates of Kos (; grc-gre, Ἱπποκράτης ὁ Κῷος, Hippokrátēs ho Kôios; ), also known as Hippocrates II, was a Greek physician of the classical period who is considered one of the most outstanding figures in the history o ...
' essay ''On Airs, Waters, and Places''. In it, he urges physicians to contemplate how factors such as drinking water can impact the health of their patients. Another famous example of environment-health interaction is the
lead poisoning experienced by the
ancient Romans
In modern historiography, ancient Rome refers to Roman civilisation from the founding of the city of Rome in the 8th century BC to the collapse of the Western Roman Empire in the 5th century AD. It encompasses the Roman Kingdom (753–509 ...
, who used lead in their water pipes and kitchen pottery.
Vitruvius
Vitruvius (; c. 80–70 BC – after c. 15 BC) was a Roman architect and engineer during the 1st century BC, known for his multi-volume work entitled '' De architectura''. He originated the idea that all buildings should have three attribut ...
, a Roman
architect
An architect is a person who plans, designs and oversees the construction of buildings. To practice architecture means to provide services in connection with the design of buildings and the space within the site surrounding the buildings that h ...
, wrote to discourage the use of lead pipes, citing health concerns:
"Water conducted through earthen pipes is more wholesome than that through lead; indeed that conveyed in lead must be injurious, because from it white lead is obtained, and this is said to be injurious to the human system. Hence, if what is generated from it is pernicious, there can be no doubt that itself cannot be a wholesome body. This may be verified by observing the workers in lead, who are of a pallid colour; for in casting lead, the fumes from it fixing on the different members, and daily burning them, destroy the vigour of the blood; water should therefore on no account be conducted in leaden pipes if we are desirous that it should be wholesome. That the flavour of that conveyed in earthen pipes is better, is shewn at our daily meals, for all those whose tables are furnished with silver vessels, nevertheless use those made of earth, from the purity of the flavour being preserved in them"
Generally considered to be one of the founders of modern
epidemiology
Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in a defined population.
It is a cornerstone of public health, and shapes policy decisions and evide ...
,
John Snow conducted perhaps the first environmental epidemiology study in 1854. He showed that London residents who drank sewage-contaminated water were more likely to develop
cholera than those who drank clean water.
U.S. government regulation
Throughout the 20th century, the United States Government passed legislation and regulations to address environmental health concerns. A partial list is below.
Precautionary principle
The
precautionary principle
The precautionary principle (or precautionary approach) is a broad epistemological, philosophical and legal approach to innovations with potential for causing harm when extensive scientific knowledge on the matter is lacking. It emphasizes caut ...
is a concept in the environmental sciences that if an activity is suspected to cause harm, we should not wait until sufficient evidence of that harm is collected to take action. It has its roots in German environmental policy, and was adopted in 1990 by the participants of the North-Sea Conferences in The Hague by declaration.
In 2000, the
European Union
The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been de ...
began to formally adopt the precautionary principle into its laws as a Communication from the
European Commission
The European Commission (EC) is the executive of the European Union (EU). It operates as a cabinet government, with 27 members of the Commission (informally known as "Commissioners") headed by a President. It includes an administrative body ...
. The United States has resisted adoption of this principle, citing concerns that unfounded science could lead to obligations for expensive control measures, especially as related to greenhouse gas emissions.
Investigations
Observational studies
Environmental epidemiology studies are most frequently
observational
Observation is the active acquisition of information from a primary source. In living beings, observation employs the senses. In science, observation can also involve the perception and recording of data (information), data via the use of scienti ...
in nature,
meaning researchers look at people's exposures to environmental factors ''without intervening'' and then observe the patterns that emerge. This is due to the fact that it is often unethical or unfeasible to conduct an
experimental study of environmental factors in humans. For example, a researcher cannot ask some of their study subjects to smoke
cigarettes to see if they have poorer health outcomes than subjects who are asked not to smoke. The study types most often employed in environmental epidemiology are:
*
Cohort studies
A cohort study is a particular form of longitudinal study that samples a cohort (a group of people who share a defining characteristic, typically those who experienced a common event in a selected period, such as birth or graduation), performing ...
*
Case-control studies
*
Cross-sectional studies
In medical research, social science, and biology, a cross-sectional study (also known as a cross-sectional analysis, transverse study, prevalence study) is a type of observational study that analyzes data from a population, or a representative su ...
Estimating risk
Epidemiologic studies that assess how an environmental exposure and a health outcome may be connected use a variety of
biostatistical approaches to attempt to quantify the relationship.
Risk assessment
Broadly speaking, a risk assessment is the combined effort of:
# identifying and analyzing potential (future) events that may negatively impact individuals, assets, and/or the environment (i.e. hazard analysis); and
# making judgments "on the ...
tries to answer questions such as "How does an individual's risk for disease A change when they are exposed to substance B?," and "How many excess cases of disease A can we prevent if exposure to substance B is lowered by X amount?."
Some statistics and approaches used to estimate risk are:
*
Odds ratio
An odds ratio (OR) is a statistic that quantifies the strength of the association between two events, A and B. The odds ratio is defined as the ratio of the odds of A in the presence of B and the odds of A in the absence of B, or equivalently (due ...
*
Relative risk
*
Hazards ratio
*
Regression modeling
*
Mortality rate
Mortality rate, or death rate, is a measure of the number of deaths (in general, or due to a specific cause) in a particular population, scaled to the size of that population, per unit of time. Mortality rate is typically expressed in units of d ...
s
*
Attributable risk In epidemiology, attributable risk or excess risk is a term synonymous to risk difference, that has also been used to denote attributable fraction among the exposed and attributable fraction for the population.
See also
* Population Impact Measu ...
Bradford Hill criteria
To differentiate between
correlation and causation, epidemiologists often apply a set of criteria to determine the likelihood that an observed relationship between an environmental exposure and health consequence is truly causal.
In 1965,
Austin Bradford Hill
Sir Austin Bradford Hill (8 July 1897 – 18 April 1991) was an English epidemiologist and statistician, pioneered the randomised clinical trial and, together with Richard Doll, demonstrated the connection between cigarette smoking and lung ...
devised a set of postulates to help him determine if there was sufficient evidence to conclude that cigarette smoking causes lung cancer.
The
Bradford Hill criteria are:
# Strength of association
# Consistency of evidence
# Specificity
# Temporality
# Biological gradient
# Plausibility
# Coherence
# Experiment
# Analogy
These criteria are generally considered to be a guide to scientists, and it is not necessary that all of the criteria be met for a consensus to be reached.
See also
*
Epidemiology
Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in a defined population.
It is a cornerstone of public health, and shapes policy decisions and evide ...
*
Occupational epidemiology
Occupational epidemiology is a subdiscipline of epidemiology that focuses on investigations of workers and the workplace. Occupational epidemiologic studies examine health outcomes among workers, and their potential association with conditions in ...
*
Envirome
*
Environmental health
Environmental health is the branch of public health concerned with all aspects of the natural and built environment affecting human health. In order to effectively control factors that may affect health, the requirements that must be met in ...
*
Environmental science
*
Exposome
*
Occupational epidemiology
Occupational epidemiology is a subdiscipline of epidemiology that focuses on investigations of workers and the workplace. Occupational epidemiologic studies examine health outcomes among workers, and their potential association with conditions in ...
*
Occupational safety and health
References
Further reading
*{{cite book, editor1=Baker, D. , editor2=Nieuwenhuijsen, M.J. , title=Environmental Epidemiology: Study Methods and Application, year=2008, publisher=Oxford University Press, location=New York, isbn=978-0-19-852792-3
External links
International Society for Environmental Epidemiology"ENVIRONMENTAL EPIDEMIOLOGY''journal
International Epidemiological Association*
ttp://journals.lww.com/epidem/pages/default.aspx EPIDEMIOLOGYjournal
*
Environmental Health Perspectives' (news and peer-reviewed research journal published by the
National Institute of Environmental Health Sciences)
Environmental Health Newscurrent events in environmental health
Epidemiology
Environmental health