Think of a glass of water about millilitres. Consumed in normal quantities of say 1. Yet if you were to consume say 3 litres of water per day, you might end up with symptoms of overhydration and damaging your kidneys. Here, water can be both healthful and harmful, depending on the amount we consume. The Swiss German philosopher Parcelsus — stated that the dose is the poison sola dosis facit venenum — a statement that forms the basis of toxicology.
Everything can be hazardous. A pothole in the ground can be hazardous as a person who falls in the hole can injure himself; air can be hazardous if people inhale the toxic particulate matters; water can be hazardous if people drink too much, or if people fall in a pool.
These are hazards in the sense of the potential that they can cause harms to humans. Thus hazards are qualitative statements , and we consider any entity as a hazard if we can argue that they have a potential to cause harm.
Cigarette smoke can harm our lungs; therefore smoke is a hazard. But the risk of cigarette smoking is lung cancer among other diseases and we can state that risk only after we find evidence that cigarette smoking is associated with lung cancer.
Occupational & Environmental Health Risk Assessment
The third concept in environmental health is the difference between exposure and dose. Environment in environmental health refers to those elements in our external environment that are caused by human activities, and that these are entities are hazards in the sense that they can cause harm to our health; when they do harm our health, we can quantify the risks.
Exposure, therefore as you can see, like hazard, is a qualitative concept. The quantitative concept of exposure is dose. Think about drinking a glass of contaminated water. Does that mean that person will immediately suffer from harm?
If the dose is low, even with exposure, the harm may not occur, so the hazard will not result in risk. Dose therefore refers to the amount of the toxin that reaches the target organ ready to exert its effect. So, the pathway goes something like. As we see in the above pathway, a hazardous object in the environment enters the body through exposure pathways, and exerts an effect on the tissue s when sufficient quantities of it accrue or are present.
Speaking of biochemical or biological agents, this exertion of the hazard on the body by affecting body tissues is referred to as toxicokinetics of the exposing agent. The body, in turn, acts on the hazard and will modify or excrete or eliminate from the body. The action of the body on the hazardous object is referred to as toxicodynamics of the body on the agent.
A balance between the toxicokinetics and toxicodynamics of the agent and the body on each other will determine how much of the toxic agent can exert its action on the body and how much the body can act to nullify it or remove it from the body and the net result is the health effect. So far, we have seen that anything in our external environment can be a hazard or health hazard ; the health hazard enters the body through one or more exposure pathway s and exerts its action on the body to result in health effects.
But how do we know in the first place an agent in the environment is a health hazard? How would we know that contaminated air or water or food that we have consumed has resulted in disease? How much of all diseases can be attributed to environmental variables? You can answer such questions by conducting Environmental Epidemiological studies.
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Environmental epidemiology refers to the study of distribution of diseases in populations where the determinants of such diseases are environmental. As we move from hazard to risk, we traverse two paths that are serially linked: first, we must identify the hazard and second, we must characterise the risk.
Think of a slippery pavement. We identify this to be a hazard to health: people can slip on a slippery pavement and break their hips if slippery pavement is a hazard, then hip fracture is the risk of walking on a slippery pavement.
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But how much of a risk is associated with a slippery pavement? Ralis conducted a study on icy pavements and risk of hip and other bone fractures in Cardiff, Wales in ; he studied patients who reported with fractures resulting from fall from walking on icy pavements on days when it snowed and compared it with what he termed as control periods or chosen days when it did not snow and calender days a year later.
An illustrative graph shows the results:. These figures suggest that snow and ice days that result in icy pavements are risk factors for hip fractues and therefore icy pavements are hazardous to health. You may wonder what makes this an environmental epidemiological study if snow and ice storms cannot be human engendered. Can you think of how the human element in modification of environment comes into consideration of how people can slip and fall on icy pavements? In any case, enviromental epidemiological studies like this enable us to move from conceptualisation of a hazard slippery pavement to actually identifying the risk of hip fracture.
While icy pavement is considered a health hazard as presence of hard ice on footpath can be so slippery that anyone can fall, but the risk still needs to be quantified. To recapitulate, epidemiology is defined as the study of the distribution and determinants of health related states and use of this knowledge for prevention of illnesses and for advancement of health health promotion.
In the context of environmental epidemiology, we specifically look at environmental factors as exposure and we compare people with and without specific health states or people with and without specific exposure and then compare exposure or health states. Based on the findings of the studies we build the evidence on the linkage between environmental factors and health effects.
Therefore understanding principles of epidemiology is critical for environmental and occupational health in testing explanations and theories that underlie the observations we make. For example, in s, doctors in the West Bengal state of India observed many patients who reported to them with signs of dark and white pigments in their palms and on their hands.
Many of these patients were people who worked in farms and had for years consumed water they pumped from shallow tubewells see the following figure :. Abstract: Onehallmark of sepsis is a reduced number of lymphocytes, termed lymphopenia,that occurs from decreased lymphocyte proliferation or increased cell death contributing to immune suppression.
Histone modification enzymes regulate immunity by epigenetically modulating chromatin architecture, however, the role of these enzymes in lymphopenia remains elusive. PRMT4 inhibition with a small molecule compound attenuated lymphocyte death in complementary models of sepsis. These findings demonstrate a previously uncharacterized role of a key chromatin modulator in lymphocytesurvival that may shed light on devising unique therapeutic modalities to lessen severity of septic immunosuppression.
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Pursue a career in environmental and occupational health Doctoral degree graduates are prepared to work in laboratory-based academic settings as faculty or postdoctoral fellows and become prominent members of government agencies and independent industries. HALL, S. Use of ultraviolet- fluorescence based simulation in evaluation of personal protective equipment worn for first assessment and care of a patient with suspected high consequence infectious disease.
The Natural Hazards Partnership: a national public-sector collaboration in the UK for natural hazard disaster risk reduction. Metal worker's lung: spatial association with mycobacterium avium. Tools and techniques in risk assessment in public risk management organisations. Risk-based reboot for global lab biosafety. Analysis of soluble or titanium dioxide derived from titanium levels in human whole blood : consensus from an inter-laboratory comparison. LEE, T. Laboratory comparison of new high flow rate respirable size-selective sampler.
British rubber and cable industry cohort: year mortality follow-up. A Computational workflow for probabilistic quantitative in Vitro to in Vivo extrapolation. Deflagrations of localised homogeneous and inhomogeneous hydrogen-air mixtures in enclosures. Evaluation of a shortened qualitative fit test method for filtering facepiece respirators. Background levels of microorganisms in busy urban environment of transport hubs.
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The development of methods to measure exposure to a major rabbit allergen Ory c 1. Dustiness de nanomateriaux en poudre: proposition d'un nouvel indice relatif a la metrique surface Dustiness of nanaomaterial in powder form: proposal of a new surface-based dustiness index. Dustiness de nanomateriaux en poudre: inter-comparaison de quatre methodes [Dustiness of nanomaterial in powder: inter-comparison of four methods]. Evaluation of the effectiveness of tool timers for estimation of daily exposure time to hand arm vibration.