Assessment Of Toxicity Of Chlorine Solution Biology Essay


The appraisal of toxicity of Cl was carried out on Escherichia coli ( E. coli ) utilizing the ToxTrak toxicity trial ( DR/4000 Procedure ) . The Cl plays many of import functions in medical scientific discipline. It is besides used as germicide. This method is a colorimetric trial based on the resazurin decrease by the respiration procedure of bacteriums. The resazurin is a redox-active dye. It is bluish colour dye but when it is reduced, it shows pink colour. The alteration in colour from bluish to tap is depends upon the bacterial respiration. The rate of decrease of resazurin can be inhibited by the toxic substances. The function of chemical gas pedal was to rush up the rate of reaction ( ToxTrak Test press release ) . The initial and concluding optical density was measured utilizing tintometer at 603 wavelengths. Using the appropriate expression, the % suppression ( percent suppression ) for different ten-fold solutions ( 100 % , 10 % and 1 % solutions ) was calculated. The sample 1 with 100 % solution of Cl shows 107.9 % suppression, the sample 2 with 10 % Cl solution shows 99.8 % suppression and sample 3 with 1 % Cl solution shows 70 % suppression. It shows increase in % suppression with the addition of chlorine concentration. The consequence shows biocide consequence of different concentration of chlorine toxicity on bacteriums. The ToxTrak Test used to mensurate the toxicity of chemical compound on different species and beings.


Chlorine plays many of import functions in medical scientific discipline, as germicides, and it is besides a component of medical specialties. The trichloromethane was the first anaesthetic used during surgery. Chlorine affectional against disease doing micro-organisms that is the ground, that it is used as germicide in imbibing H2O, swimming pool, and besides in effluent intervention works. It is besides used to disinfect surfaces by utilizing bleach. Bleach consists of Cl in the gaseous signifier which is dissolved in an alkali-solution. The mechanism of action of Cl on micro-organisms is to impact the bacteriums and viruses on their chemical bonds in their molecules. The germicides consist of Cl compounds that can interchange atoms with other compounds, for illustration, enzymes in bacteriums. When Cl comes in contact with enzymes, it replaces the H in the molecule and it consequences in alteration in the form of molecule and finally it falls apart. The 0.2-0.4 mg/L of Cl is adequate to kill the bacterium. The factors impacting the affectivity of Cl are Chlorine concentrations, continuance of exposure, temperature, pH, and figure and types of micro-organisms that are exposed ( ) .

Table: 1 The disinfection clip for different micro-organisms with chlorinated H2O.

Chlorine concentration = 1 mg/L or 1 ppm, pH = 7.5 and T = 25 & A ; deg ; C. ( )

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Organisms Name Duration of disinfection

Cryptosporidium spp.

6-7 yearss

Giardia parasite

40-45 proceedingss

Hepatitis A virus

15-16 proceedingss

Escherichia coli 0157 H7 bacteria

Less than 1 minute

The reaction of Cl on human organic structure depends on assorted factors like, the concentration of Cl, the continuance and frequence of exposure to the Cl compound. It can besides depend on the wellness of a individual and the environment during the exposure. The exposure to chlorine or chlorine compound can impact the respiratory system. The effects vary from coughing, thorax strivings, and accretion of fluid in the lungs. It can besides do skin annoyance and oculus annoyances upon exposure. The Cl in the pure signifier can be really toxic. Even the little sum of pure Cl can be lifelessly to the person. The Cl is much denser than the air. Chlorine gas affects the mucose membrane of nose, pharynx, and eyes. It is really detrimental to mucose membranes as it dissolves them ( ) .

The WHO criterions for imbibing H2O set the sum of Cl is 2-3 mg/L and it gives a satisfactory disinfection of H2O. The WHO set the maximal sum of Cl that is used by people is 5 mg/L. The national imbibing H2O criterions set the sum of Cl in residuary country is 4 mg/L ( ) .

Materials and Method:

The ToxTrakaµˆa?? toxicity trial was used to find the % of suppression ( percent suppression ) of Escherichia coli after exposed to different ten-fold concentrations of chlorine solutions. The family Cl bleach was used during the experiment. One twenty-four hours before the experiment, the inoculant was prepared. The beginning civilization of E. coli was transferred by utilizing the sterilized dropper pipets of 1.0 milliliter into the lauryl tryptose broth tubings. The tubings were incubated at 35 & A ; deg ; C until the vial contents shows turbidness ( bacterial growing ) . On the following twenty-four hours, the 10 milliliter of trial tubings were labeled and prepared by adding the appropriate sum of deionized H2O, chlorine solution ( household bleach ) , gas pedal, reagent pillows and E. coli inoculants as shown in Table 2 ( DR/4000 Procedure press release ) .

Table 2 Preparation of trial tubings:

After the readying of tubings, the readings were recorded utilizing the spectrophotometer at a wavelength of 603 nanometers and the optical density was adjusted to 0.00 Abs. The initial optical densities for all four tubings were recorded and than all the tubings were allowed to respond. The optical density of control was checked often until it shows decreased in Abs to at least 0.06 than the old recorded Abs. The lessening in the Abs normally takes 30-45 proceedingss. The reaction of resazurin decrease gives the lessening in optical density. The resazurin is the oxidation-reduction dye and it gave bluish colour to command and samples in its oxidised signifier. The bacteria start utilizing the food from the stock and it convert the resazurin in its decreased signifier and finally it gave pink colour to the tubings. The transition of bluish to tap shows the respiration procedure of bacteriums and besides the use of glucose in the beef infusion reduced the resazurin compound. After 30 proceedingss of reaction, the optical density was measured once more. The spectrometer was adjusted to 0.00 utilizing the space and so the tubings were placed one by one and the optical densities were recorded for each tubing ( DR/4000 Procedure press release ) .

The % suppression ( percent suppression ) was calculated for control and the sample tubings utilizing the below expression ;

% I ( percent suppression ) = [ 1 – a?†A sample & A ; divide ; a?†A command ] – 100

Where, a?†A= Initial optical density value- Final optical density value.


The initial and concluding optical densities were recorded in the Table 3 and besides the % suppressions for samples and control was recorded. The consequences are as seen below in Table 3.

Table 3 Initial and concluding optical density and % suppression for Control and Sample tubings.

The graphical representation of the consequences is shown below ;

Graph 1: It shows the initial and concluding optical density differences in each ten-fold Cl sample solutions.

Graph 2: It shows the % suppression of sample solutions.


The consequence shows the highest per centum suppression in the sample 1 with 100 % of chlorine solution ( Table 3 ) . The gradual lessening in the % suppression can be seen in all the samples from sample 1 to try 3 as seen in Graph 2. The graphical representation of consequences is easy to construe the informations and it shows that the consequence support the aim of the survey.

The alteration in colour from bluish to tap in the sample and control solution was the transition of resazurin in to its decreased signifier. The reagent pillow contains resazurin, beef infusion, 4- morpholinepropane sulfonic acid, 4- morpholinepropane sulfonic acid Na salt, peptone, and Na ethanoate. The resazurin is the oxidation-reduction dye and it show bluish colour in its oxidised signifier. The bacterium oxidise the glucose and it reduces the resazurin. The resazurin reduced and signifier resafurin, which is pink. Further decrease of this compound gives colourless solution which has dihydroresofurin. The substances or chemicals that are toxic to the bacteriums can suppress the rate of their metamorphosis and therefore suppress the rate of decrease of resazurin. The gas pedal is the solution of glutaric dialdehyde and H2O which increase the rate of reaction or cut down the reaction clip of sample solutions and control. As expected, the sample 1, 2 and 3 shows positive per centum metabolic suppression in E. coli. The % suppression of Cl additions with the addition in the ten-fold concentration of Cl in the sample solutions ( Result Table 3 ) .


The consequences of the experiment of appraisal of toxicity of Cl by utilizing the ToxTrak trial method suggest that the chlorine solution ( household bleach ) is really effectual for bacteriums like E. coli. as biocides at really low concentration.