Toxic Heavy Metals

Toxic Heavy Metals

(Source: caobisco)

1. Lead (Pb)

· The main sources of lead pollution in the environment are: Industrial production processes and their emissions, road traffic with leaded petrol, the smoke and dust emissions of coal and gas-fired power stations, the laying of lead sheets by roofers as well as the use of paints and anti-rust agents.

· Lead can trigger both acute and chronic symptoms of poisoning. Acute intoxications only occur through the consumption of relatively large single doses of soluble lead salts.

· In 1993, the joint FAO/WHO Expert Committee for Additives and Contaminants (JECFA) reduced the value it had provisionally specified for adults in 1972, for tolerable lead consumption per week (PTWI - provisional tolerable weekly intake), from 0.05 mg/kg body weight to 0.025 mg (or 25 µg).

· The lead content in drinking water presents a problem in many countries. Thus, the present WHO guideline of 50 µg/l is exceeded in Great Britain, for example, in 34 % of households.

2. Cadmium (Cd)

· Cadmium (world production in 1972, 15 000 t) exists in low concentrations in all soils. It is actively extracted from its ores for commercial purposes and is also emitted in industrial processes such as metal melting and refining, coal and oil-fired power stations, electroplating plants, etc.

· Cadmium is today regarded as the most serious contaminant of the modern age. It is absorbed by many plants and seacreatures and, because of its toxicity, presents a major problem for foodstuffs. Contamination through fertilisers becomes an increasing problem.

· Unlike lead, cadmium contamination cannot be removed from plants by washing them; it is distributed throughout the organism. It is often difficult to be certain of the cause of a cadmium content found in fruit or vegetables, as the substance in its natural form exists everywhere in the soil and is absorbed by the roots.

· Cadmium is concentrated particularly in the kidneys, the liver, the blood forming organs and the lungs. It most frequently results in kidney damage (necrotic protein precipitation) and metabolic anomalies caused by enzyme inhibitions.

· Cadmium, like lead, is a cumulative poison, i.e. the danger lies primarily in the regular consumption of foodstuffs with low contamination.

· In most countries, there are legal regulations regarding permissible cadmium contamination levels. As a rule, these are based on the PTWI value last set by the JECFA of the FAO/WHO in 1989 of about 7 µg/kg body weight, corresponding with a quantity of 0.4-0.5 mg per person (70 kg) per week.

· One problem of a special kind is the smoking of tobacco. 20 cigarettes a day provide a cadmium input of 4 µg.

3. Mercury (Hg)

· Passes into the environment through emissions from chemical plants (paints, paper, chlorine, plant pesticides) and power stations, mostly in effluents and sludge.

· Mercury becomes concentrated in shellfish, crustaceans and fish and thus also passes, in the form of highly toxic mercury methylate, into the human food chain.

· Mercury in the form of its methyl compounds is specifically the most toxic of the heavy metals.

· When consumed orally, it first passes into the liver, the kidneys and the brain.

· In the case of chronic consumption, first cause tiredness, loss of appetite and weight loss. In the end the kidneys fail. Muscular weakness and paralysis are typical.

· The FAO/WHO Expert Committee (JECFA) has set a provisional maximum acceptable value for mercury consumption at 5 µg per kg body weight per week.

4. Arsenic (As) (source)

· Arsenic is the most common cause of acute heavy metal poisoning in adults and is number 1 on the ATSDR's "Top 20 List."

· Arsenic is released into the environment by the smelting process of copper, zinc, and lead, as well as by the manufacturing of chemicals and glasses.

· Arsine gas is a common byproduct produced by the manufacturing of pesticides that contain arsenic.

· Arsenic may be also be found in water supplies worldwide, leading to exposure of shellfish, cod, and haddock. Other sources are paints, rat poisoning, fungicides, and wood preservatives.

· Target organs are the blood, kidneys, and central nervous, digestive, and skin systems (Roberts 1999; ATSDR ToxFAQs for Arsenic).

5. Others Heavy Metals

· Some heavy metals (the so-called trace elements) are essential in very small concentrations for the survival of all life forms, for example, copper, iron, zinc, chromium, molybdenum and others.

· Nickel has often been associated recently with allergies (contact with jewellery and jeans buttons containing nickel). There is no established knowledge of effects of this type when it is absorbed in the gastro-intestinal tract. Cocoa is one of the foodstuffs with higher than average natural nickel contents.

· The copper content of tomato dishes prepared in copper pots and having a copper content of 0.1-0.2 mg/kg body weight has already been found to cause digestive disturbances in sensitive consumers! This is in spite of the specified tolerable quantity for daily consumption of 0.5 mg/kg.

· Chromium, copper and zinc play major roles in modern industry and, in the vicinity of extraction or processing plants, the emissions arising are certainly capable of causing an undesirable contamination of agricultural products. Considerable quantities have been found in fruit and vegetables. However, no adverse effects on health are known. It is nevertheless recommended not to omit these metals a priori from scrutiny.

Ionizing Radiation

What is Ionizing Radiation?

Ionizing radiation is energy in the form of waves or particles that has enough force to

remove electrons from atoms (USEPA).

Radiation that falls within the ionizing radiation" range has enough energy to remove tightly bound electrons from atoms, thus creating ions. This is the type of radiation that people usually think of as 'radiation.' We take advantage of its properties to generate electric power, to kill cancer cells, and in many manufacturing processes.

and..

Radiation that has enough energy to move atoms in a molecule around or cause them to vibrate, but not enough to remove electrons, is referred to as "non-ionizing radiation." Examples of this kind of radiation are sound waves, visible light, and microwaves.

The energy of the radiation shown on the spectrum below increases from left to right as the frequency rises.

Longer wave length, lower frequency waves (heat and radio) have less energy than shorter wave length, higher frequency waves (X and gamma rays). Not all electromagnetic (EM) radiation is ionizing. Only the high frequency portion of the electromagnetic spectrum which includes X rays and gamma rays is ionizing (WHO).

What is Radon

About Radon, (source: WHO)

Radon is a chemically inert, naturally occurring radioactive gas. It has no smell, colour or taste. Radon is produced from the natural radioactive decay of uranium, which is found in rocks and soil. Radon can also be found in water.

Radon escapes easily from the ground into the air, where it

disintegrates through short-lived decay products called radon progeny. As radon progeny decay, they emit radioactive alpha particles and attach to aerosols, dust and other particles in the air. As we breathe, radon progeny are deposited on the cells lining the airways where the alpha particles can damage DNA and potentially cause lung cancer.

Outdoor radon levels are usually very low. The average outdoor radon level varies between 5 and 15 Bq/m3 [Radon radioactivity is measured in Becquerel (Bq). One Becquerel corresponds to the transformation (disintegration) of one atomic nucleus per second. Radon concentration in air is measured by the number of transformations per second in a cubic metre of air (Bq/m3)]. Indoors, radon levels are higher, with highest levels found in places such as mines, caves and water treatment facilities.

Exposure of radiation:

(Source: WHO)

How Radon enters a house?

Radon enters homes through:

• cracks at concrete floor-wall junctions
• gaps in the floor
• small pores in hollow-block walls
• sumps and drains.

(source: www.prlog.org)

Radon levels in homes can be reduced by:

• improving the ventilation of the house
• avoiding the passage of radon from the basement into living rooms
• increasing under-floor ventilation
• installing a radon sump system in the basement
• sealing floors and walls
• installing a positive pressurization or ventilation system.

(source: http://www.ab.ust.hk/hseo/sftywise/199504/page1.htm)

Risk Assessment (source)

Exposure to radon, no matter how much exposure, does not mean you will get lung cancer. The risks associated with contracting lung cancer are in relationship to the amount of time exposed and the average Radon concentration levels.

Most radiation protection specialists believe, (at a minimum), that if you are continuously exposed to levels at or above 4 pCi/L then you are at risk. The US EPA's action level for Radon is 4 pCi/L. The World Health Organization has recently suggested that the action level should be 2.7 pCi/L, 33% lower than the current EPA action level.

The EPA has identified radon exposure as the number one cause of lung cancer in non smokers, and second only to smoking overall. Smokers generally have about 10 times higher risk than non smokers. Risk assessments associated with elevated radon concentrations are considered to be linear, meaning higher levels and longer duration of exposure increase risk assessment accordingly to the increase in concentration and amount of time exposed.

EPA risk assessment data from radon exposure is based on a lifetime of exposure.

• Not everyone exposed to even high levels of radon will contract radon induced lung cancer.
• All radon levels can be lowered, which lowers the risk assessment.

read more about radon:

UNCEAR: Sources to effects assessment for radon in homes and workplaces

WHO: WHO HANDBOOK ON INDOOR RADON: A PUBLIC HEALTH PERSPECTIVE

Gamma Spectrometry - Efficiency Calculation for K-40

Gamma Efficiency for K-40

Activity

Define activity, A = Number of spontaneous disintegrations in a source in one second.

Unit of activity, A = Bq (Becquerel)

Activity, A

N = Number of atom for K40

λ = Decay constant

t = Time

Specific Activity

Half-life

λ is a decay constant, therefore

How to calculate Activity and efficiency of K40 in KCl for Gamma Spectrometry

(eg. Standard KCl, 400g was used to calibrate the gamma spectrometry)

a) Calculate Mass of K in KCl

=

b) Calculate Mass K40 in 209.779 g K

=
=
= g

c) Calculate Number of atom K40

d) Calculate Decay constant, λ for K40

e) Calculate Activity K40 in KCl

f) Efficiency K40 for Gamma Spectrometry

(eg. Counting time = 43200 s, peak area = 140 000)

Statistic - Q test

Theory

In a set of replicate measurements of a physical or chemical quantity, one or more of the obtained values may differ considerably from the majority of the rest. In this case there is always a strong motivation to eliminate those deviant values and not to include them in any subsequent calculation (e.g. of the mean value and/or of the standard deviation). This is permitted only if the suspect values can be "legitimately" characterized as outliers.

Usually, an outlier is defined as an observation that is generated from a different model or a different distribution than was the main "body" of data. Although this definition implies that an outlier may be found anywhere within the range of observations, it is natural to suspect and examine as possible outliers only the extreme values.

The rejection of suspect observations must be based exclusively on an objective criterion and not on subjective or intuitive grounds. This can be achieved by using statistically sound tests for "the detection of outliers".

The Dixon's Q-test is the simpler test of this type and it is usually the only one described in textbooks of Analytical Chemistry in the chapters of data treatment. This test allows us to examine if one (and only one) observation from a small set of replicate observations (typically 3 to 10) can be "legitimately" rejected or not.

Q-test is based on the statistical distribution of "subrange ratios" of ordered data samples, drawn from the same normal population. Hence, a normal (Gaussian) distribution of data is assumed whenever this test is applied. In case of the detection and rejection of an outier, Q-test cannot be reapplied on the set of the remaining observations.

In statistics, Dixon's Q test, or simply the Q test, is used for identification and rejection of outliers. This test should be used sparingly and never more than once in a data set. To apply aQ test for bad data, arrange the data in order of increasing values and calculate Q as defined:

Where gap is the absolute difference between the outlier in question and the closest number to it. If Q_calculated > Q_table then reject the questionable point.

EXAMPLE:

For the data:

0.189, 0.167, 0.187, 0.183, 0.186, 0.182, 0.181, 0.184, 0.181, 0.177

Arranged in increasing order:

0.167, 0.177, 0.181, 0.181, 0.182, 0.183, 0.184, 0.186, 0.187, 0.189

Outlier is 0.167. Calculate Q:

With 10 observations, Q_calculated (0.455) > Q_table (0.412), so reject it with 90% confidence. However, at 95% confidence, Q_calculated (0.455) < Q_table (0.466).

Therefore keep 0.167 at 95% confidence or reject it at 90% confidence.

TABLE

This table summarize the limit values of the test.

(sources: wikipedia, http://www.chem.uoa.gr/applets/AppletQtest/Text_Qtest2.htm)

EDXRF - Calibration

Guideline for students

The most important task that need to be completed in sample measurement is calibration of the instrument. without the calibration, the quantitative analysis can't be done and to do that, we need to get the calibration graph and their equation. this is the manual technique for carried out the calibration of the instrument. below is a technical note of standard calibration of EDXRF.

to view full page [click here]

when do the calibration, student need to do some background study about EDXRF and literature review. Further literature review about the condition of the samples, energy line measure, measured line ( K, L, M), sample preparation and others will help student more understand.

EDXRF - Periodic Table and Peak Identification

This is the Periodic Table and Peak Identification for EDXRF. It include the type of filter recommended for each element in XRF measurement and also the energy line measured for the elements. The Peak Identification is to identify the energy peak of element in the spectrum.

(to download - right click at [Download] and save as).

preview

The Periodic Table of The Elements [Download]

Peak Identification Chart [Download]

post by,

Mr Admin

General Laboratory Practice and Regulation

Here is some general practice and regulation for Blok G4 Lab. All student need to read and follow the rules given.

General

1. Bring only the necessary things in.
2. In the lab you must wear a labcoat but especially during working with instruments and chemicals. without labcoat, student are prohibit from using/conducting the instrument.
3. wear gloves when handling samples and chemicals.
4. If you wear gloves, never touch doorhandles, equipment, keyboards, computers, lightswitches etc with the gloved hand. If you don't trust it is "clean", then use a clean tissue to touch it.
5. It is strictly prohibited to eat, drink or smoke in the lab.
6. It is prohibited to write or stick comments on the lab equipment without permission.
7. It is prohibited to take chemicals, reagent without permission

Safety

1. Always read instructions on the chemicals and reagents first before using them. In case of doubt consult the labtechnician.
2. Dispose chemical/biological waste in appropraite containers
3. Special attention must be given to hazardous chemicals/reagents.
4. Wash your hands before you leave the lab.

Cleaning

1. Keep the lab tidy. Everyone has to clean lab table before leaving.
2. Everyone who used the facillities of the lab that month must help to clean it.
3. Cleaning of glassware after used
4. In case of little spilling, clean area with tissues
5. Cleaning of spilles chemicals (especially near the balances):
   Always clean spilled chemicals immediately. In case of spilling hazardous chemicals, mark but avoid the contaminated area and contact the labtechnician.

Machines

1. When you use a machine and you are not familiar with it, read the equipment instructions carefully and ask person in-charge.
2. When you want to use the on your own, you need permission from person in-charge.
3. It is not allowed to install any software on the instrument computer.
4. To save your data, please used blank CD/DVD instead of USB storage to avoid virus spread on the computer.

more will be added later if necessary..

TQ,

Mr Admin

EDXRF - student reminder

Attention to all students,

Before used EDXRF, all student must attend the training course conducted by person in-charge and will be made in group. Student who missed the training course will not be allowed to use the instrument. There is No Excuse for the time of the training course. This is to make sure all the students follow-up the training.

To book EDXRF for the measurement, please contact person in-charge to add your name in the Online Schedule one week advance before the date. Before that, please check at the Online Schedule for the availability of the day you want to use it. The Information that needs to be submitted to the person in-charge is:

1. Name
2. ID
3. Program
4. H/P no.
5. Main Supervisor name
6. sample type
7. Date and time

The date and time need to be discuss with the Person In-charge and can be change without prior of notice.

The Online Schedule can be view at http://radiokimia.blogspot.com/p/schedule.html

Every week, one person in-charge will take over and will always change every week. In order for the EDXRF to operate, the person in-charge needs to be present for safety and monitoring reason. Current person in-charge:

1. Miss Linda
2. Mr Najif
3. Mr Admin

TQ,

Mr. Admin

Software

To download the software, please right click at [Download] and save as.

1. Gamma Spectrometry software

GammaVision V6.07

[Download]

2. EDXRF software

• For MiniPal software, Download All Part for complete software.

MiniPal Software

Part 1 [Download]

Part 2 [Download]

Part 3 [Download]

Part 4 [Download]

3. Mapping software

Surfer-8

[Download]

4. statistic_analysis_software

XLSTAT_PRO
[Download]

Gamma Peaks U and Th

Preview

To fully view of this document [click here]

EDXRF Principle

(Source figure)

Figure 1 show the principle of XRF, An inner shell electron is excited by an incident photon in the X-ray region. During the De-excitation process, an electron is moving from a higher energy level to fill the vacancy created by ab ejection. the energy difference between the two shells appears as an X-ray emitted by the atom. the energy of the peaks lead to the identification of the elements present in the sample (qualitative analysis), while the peak intensity provides the relevant or absolute elemental concentration (semi quantitative/quantitative analysis).

Type of radiation and their penetrating powers

(Source: Radiation Emergency Medicine Information network, REMnet)