Dose Response Figure LD50 Biology Essay

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Chemical A instantly demonstrates a NOEL of the experimental dose where a negative measurable effect is observed, this is seen through there being no effect from the beginning of dose at 5mg kg-1. The likely reason to why no reaction was experienced could be due to the concentration of the dose which failed to recognize any mortality; moreover the outcome at this stage in the body could be due to there being no enzyme inhibition of the substance. From analysing the graph you are able to see that Chemical B generates more effect than visualised in chemical A at the start of dosage, producing a direct effect within the individual. The direct effect from chemical B is illustrated through a NOAEL at 5mg kg-1of a response at 6%, though the effect of this substance is not adverse and doesn't present harm within the individual's body. In addition to this, it could be said that 'the body's ability to compensate the following exposure to the toxic chemical is surpassed'.1

The curve of chemical B gradually rises but then at 20 mg kg-1 there is a sudden slope which is fairly deep, presenting that the reaction to the chemical proceeds at a greater rate, from analysing the curve it is evident to come to the decision that chemical B is highly potent than chemical A having a lethal dose of 20 mg kg-1, thus showing that it takes less of substance B to induce an increasing response on the individual.

Maximum efficacy of chemical B is less than that of chemical A as the cumulative response is shown to be 75% whereas for chemical A it is at 100%. Chemical B is revealed to be superior to chemical A as it has a higher toxicity where death is experienced at a faster rate. On the other hand the maximal response of death occurs gradually at a much slower rate for chemical A, proving this potency. When measuring potency, the strength of the toxic chemical is being measured in comparison to other poisons. The stronger the poison the less it takes to kill, however the weaker the poison the more of the chemical it takes to kill.

The LD50 for chemical B is approximately 16mg kg-1 illustrating that it is a highly toxic substance. Chemical A can also be seen as highly toxic as it has a LD50 of 17mg kg-1; in this case it is apparent that chemical B is slightly stronger in toxicity than chemical A, classifying it as more potent, by a difference of 1mg kg-1 this minimal difference allows the substance to produce a stronger and rapid effect.

Chemical A + B together produce an increasing effect then that seen for the two chemicals independently. As both chemicals individually have a high toxicity, when combining them the result will surely produce an elevated response. The maximal efficacy of chemical A and B combined is at a cumulative response of 100% which is experienced from the dose response of 20 mg kg-1, the speedy effect produced is due to the high toxicity of both chemicals when put together.

Chemicals that have large LD50's produce poor health at small exposure levels, however it can be seen wrong to say that chemicals which exert a small LD50 are more dangerous, which in this case are chemical A and chemical B, but the fact is that they are simply more toxic. Comparing the toxicity and safety of each chemical based on results shown in figure 1 can sometimes be seen as not enough; as this is an over simplified approach to analysing the data and comparing the chemicals because the LD50 figure is merely one point on the dose response curve which portrays the potential of the compound to cause death. Even though the LD50 can provide some vital information it is limited in the sense that it only reflects the information about the lethal effects of the chemical. There is possibility that the chemical will produce an undesirable venomous outcome at doses which actually cause no death.


A.S.Kane (2007), Dose response concepts [Online]. Available from: [Date Accessed: 14th July 2012]

Conde SV, Gonzalez C, Batuca JR, Monteiro EC, Obeso A (2008), An antagonistic interaction between A2B adenosine and D2 dopamine receptors modulates the function of rat carotid body chemoreceptor cells [Online]. Available from: [Date Accessed: 14th July 2012]

2)  Research food additives and their effect on human health focusing on recent reports of possible effects for which there is tentative data. Write a brief report of your findings, by answering the following questions:

Food additives consist of chemicals which are added to various foods to improve its appearance, flavour or to expand shelf life. There are presently hundreds of additives existent and the one I have researched in particular is the colourant E102; also knows as Tartrazine.

Tartrazine is a yellow synthetic food dye made from coal-tar derivatives and is found in numerous different foods including puddings, cake mixes, soups, ice creams, jams and sweets. It is also found in the shells of a range of medicines. Often it is further mixed with E133 to produce various green shades which is then used for tinned produce such as peas.

In recent years, The FSA (Food Standards Agency) in Britain released a warning about E102 and other food dyes highlighting the possibility of a strong link with the additive and the causation of hyperactivity and loss of concentration in children today. The FSA further stated that they recommend parents to restrict the use of any products which contained this dye. Furthermore, a study at Southampton University in September 2007 'investigated the effects of six colors - Tartrazine, Quinine Yellow, Sunset Yellow FCF, Carmoisine, Ponceau 4R and Allura Red. (European codes E102, E104, E110, E122, E124 and E129)'1. The researchers involved estimated that a ban to the above food colourants could prevent approximately 30% of Attention Deficit Hyperactivity Disorder (ADHD) cases. The Hyperactive Children's Support Group also believes that a link exists.

Moreover it has been reported that people who are sensitive to tartrazine- fatigue, headaches, depression and sleeping problems have all been present. Also, it has been known to be a trigger for asthma, as people with this condition have been particularly sensitive to this food dye, and it can also be triggered by aspirin intolerant patients. Other side effects of this additive include eczema, anxiety, blurred vision, hives and other skin rashes, and thyroid cancer. Before further research was conducted on E102, suggested side effects which linked consumption to effects on male potency, penis size and sperm count. However, this was not confirmed by scientific research and remained untrue.

Evidence that conveys the side effects of tartrazine is reflected in the regulation of the food dye across the world. In Europe, tartrazine was banned in Norway, Germany and Austria until this ban was overturned by an EU directive. In the USA, the law requires that if the additive is used, it should be declared on all food products and be preapproved by the FDA.

The reason that tartrazine is widely used derives from the fact that it is a cheaper alternative to beta-carotene, which is natural yet more expensive for production companies to use. Overall, tartrazine (E102) has been founded to be harmful and should be avoided when buying certain produce.


3) What were the key health concerns that lead to widespread use of tubewells in Bangladesh and what technologies could be applied to alleviate the problem?

The discovery of arsenic contamination in the groundwater through several areas of Bangladesh stimulated extensive health concerns. Arsenic is a chemical agent that is highly toxic; in water this agent is relatively soluble and occurs naturally in the environment. A high level of this toxic agent is found in a type of rock known as pyrite, in the alluvial regions of Bangladesh. Pyrite is exposed into the atmosphere as groundwater is extracted; through this process arsenic from pyrite is released which in turn causes contamination to the water supply.

Eating, drinking and breathing are the three main processes which lead to the exposure of this vicious toxin within humans. An excessive ingestion of this agent will lead to severe human health problems which include cancers to the skin, lung and bladder. Individuals with poor nutrition and socio-economic status are more susceptible to the poisoning of arsenic which results in a disease called arseniciosis.

Other key health problems which caused concern through Bangladesh are that of diarrhoea and the rise in chronic water borne diseases, through foreign pathogens, from the consumption of contaminated water. Those people living in the poorer regions of the country become highly vulnerable to severe effects of this condition. Diarrhoeal diseases are prevalent in areas of Bangladesh due to the deficiency of water and sanitation infrastructure.

In order to protect individuals and save those from deteriorating because of diseases spread through polluted surface water and the effects of arsenic, the Bangladesh Government and international development agencies developed thousands of deep tubewells around the country. The wells were suitable and free from any harmful contamination, therefore improving health throughout Bangladesh.

The specific use of technologies can be applied in order to alleviate the health concerns due to arsenic. Arsenic can be improved through the use of arsenic removal technologies, some of these technologies put into place are oxidation and the arsenic removal unit.

Oxidation is a treatment method which is highly effective in the removal of arsenic in groundwater. This process is a pre-treatment stage for the conversion of arsenite to arsenate. Arsenite can be oxidized by agents such as oxygen, free chlorine, hydrogen peroxide and also fulton's reagent. The oxidation procedure converts predominantly non-charged arsenite to charged arsenate, which is easily removable from water.

The arsenic removal unit which is attached to a tubewell is another technical process used to alleviate the amount of arsenic spiralling in groundwater. This procedure is performed through alum coagulation, sedimentation and filtration. These processes have been employed in compressed units for water treatment in the required regions of Bangladesh. The method is performed by the arsenic removal plant being attached to a tubewell. The treatment route involves installing a manually operated mixer with incorporated flat blade impellers. The tank is filled with arsenic contaminated water with the addition of the required amount of oxidant and coagulant. The water is then mixed for 30 seconds through the rotation of the mixing device; the water is then left overnight for sedimentation to occur. The water which has settled is then strained through a pipe which is fitted at a level that is a few inches from the bottom of the tank, passing through a sand bed. The water is finally collected through a tap for safe drinking. The procedures of mixing and flocculation are highly effective in the removal of toxic arsenic.

Following these technological processes should decrease the quantity of arsenic contained in water when consumed, preventing the high risk of human health problems within the individuals of Bangladesh.

4) What are the long term consequences of persistent malnutrition on a community?

Malnutrition is a condition which results from the consumption of an unbalanced diet, where the essential nutrients needed to sustain normal biological processes and functions within the body are in shortage, excessively built up or have been consumed in the wrong proportions. The effects of malnutrition are highly dependent on the types of nutrients that are under or over abundant in the diet. Consequences that lie with malnutrition can have severe long term effects on an individual.

This condition is a well recognized health problem which is extensively spread throughout less economically developed countries (LEDC's), where malnutrition is presented in the form of under nutrition, as the diet of individuals lacks the adequate vitamins, minerals, calories and proteins in order to maintain a healthy and functional system. Children and adolescents are particulary vulnerable to the long term effects of malnutrition as the body is still at the stage of development, so shortage of certain nutrients can have major drawbacks and result in lifelong health problems.

One of the highly experienced long term effects of malnutrition is caused by the lack of calcium, vitamin D and phosphate in the diet, the shortage of these vitamins and minerals lead to irreversible changes in the body's cells and tissues, where the muscles and bones within the individual slowly start to deteriorate and stunted growth will occur. The muscle and bone loss will mean that these individuals will become highly vulnerable and fragile, where even one trip or fall will result in a broken bodily part and then the healing process of this incident will prolong due to the lack of adequate vitamins and calcium; which is needed to strengthen bones, within the body.

Brain damage is another vital long term defect of malnutrition. The lack of sufficient nutrients from an early age will result in the under development and growth of the brain. Childhood is the main critical period to gain nutrients for the necessary formation of brain cells and brain development along with the neurological development within the brain. Nutrition and stimulation is the foundation for the structure of a child's brain, with the absence of one of these two requirements the brain will become abnormally functioned leading to an irreversible condition, having a lifetime effect on the individual.

Lacking the essential vitamins and minerals which assist the body's ability to fight infection will in turn disrupt the developing of the immune and nervous system within the victims faced by malnutrition; especially children as their immune systems haven't fully developed at this stage. This disruption of the immune system will lead to children becoming more susceptible to viruses and diseases which may follow from the effects of malnutrition within the community and later in life. The main reason for this factor is because their immune system will have lost function as the appropriate cells and antibodies needed to fight against these foreign pathogens have not been developed to an appropriate level. This lack of development will create a long term effect on the individuals as being in a LEDC they are more prone to harmful enteric infections and diseases.

In less economically developed countries with malnutrition HIV is common. The increasing risk of HIV transmission is from mother to child through breast feeding, the increasing replication of the virus is through direct contact of sexual intercourse. In these communities and areas which lack access to safe and clean drinking water, these additional health risks presents a critical long term effects as HIV leads to unfortunate death.

In nations and communities which are wealthier, malnutrition is most likely to result through the over nutrition and unhealthy diets caused by excess energy, fats and refined carbohydrates. Over consumption of these particular nutrients can lead to obesity. The growing trend of obesity is a major public health concern as becoming excessively overweight can lead to long term consequences such as cardiovascular disease, stroke and diabetes.

The failure to intake the appropriate nutrients required by the body in adequate amounts will slowly result in death.