Mercury Regulation and Standards

I made short of compilation, gathering information related to mercury regulation, standards, for its presence in water, fishes and other sites for many countries. However, I believe this information is extremely uncomplete. There is not much information I can find of mercury regulation in the internet, thus the information below is very limited to some countries. I will update if I find another mercury-related regulation for these and another countries. For the mean time, if you, the reader, have some information regarding this regulation, please kind share it with me, links, or info in pdf, your contribution would be much appreciated. Thank you.

Mercury standards in America

Carcinogens

What is definition of carcinogens?
What are mechanisms of actions?
What are the sources of carcinogens?
How can we identify and classify carcinogens?

What is definition of carcinogens?
It is any cancer-causing substance, chemical or physical, such as benzene, cadmium, asbestos or certain types of radiation. The term cancer refers to a type of neoplasm, defined as a new growth (plasia). Cancer is a type of neoplasm characterized by tissue undergoing rapid and abnormal growth. Tissues that grow faster tan the surrounding tissue form an enlarged mass of cells referred to as tumor.

Teratogens

What is the mechanism of teratogenic action?
What are teratogenic agents? 

The most dangerous effect of exposure to a toxic substance occurs when it impacts fetal development and the birth of a child. At birth, the number of children identified as having either a major or minor malformation is approximately 5 percent. Toxic agents that cause abnormal development resulting in birth defects are referred to teratogens.

Mutagens

How many kinds of mutations?
Is it possible for DNA restoration? 

How many kinds of mutations?
There are several types, they are spontaneous mutations, induced mutations, large and point mutations, somatic and germinal mutations.

Spontaneuos mutations
Mutations that occur without the introduction of an exogenous (outside) mutagenic agent. Various types of chemical reaction in the cell may cause these types of mutations. This type of mutation can be caused by the broken of sugar-four bases by chemical intermediates (superoxide, OH radicals, hydrogen peroxide) produced during metabolism, deamination, methylation, some mistakes made by endogenous enzyme in replicating DNA, and some additions or deletions of bases during DNA replication (may occur when there are short complementary base sequences located in the same DNA strand).

How UV can cause skin cancer

UV is a physical agent that can cause mutation of our skin. UV from the sun is known to cause cancer as a result of prologed exposure. UV radiation affects the bonds between adjacent pyrimidines located on the same or opposite DNA strands. When this happens, thymine, for example, will bond to thymine forming a T-T dimer called cyclobutyl thymine. Radiation also causes single strand breaks, double strand breaks and various types of DNA base damage.

Single strand breaks are more easily repaired by the intracellular DNA repair mechanism. While when a double strand break, there are three possible outcomes: 1) the molecule will be connected with no errors, 2) the molecule is repaired incorectly and produces a mutated DNA molecule, or 3) the DNA molecule is not repaired. A DNA molecule with a double strand break results in fragmentation of the chromosomes followed by an abnormal distribution of chromosomes during cell division. This is cancer.

Reference:
Kent, C. 1998. Basics of Toxicology. John Wiley & Sons, Inc. New York

Excretion (Ekskresi)

What is excretion?
What are the organs for excretion?

What is excretion?
Excretion is the process of eliminating waste products of metabolism and other materials that are of no use. The rate at which excretion of toxic substances occurs is important in determining the toxicity of a substance. The faster a substance is eliminated from the body, the more unlikely a biological effect will be.

What are the organs for excretion?
The primary organs involved in excretion are the kidneys, liver and lungs. Minor amounts of substances may leave the body through sweat or milk, they may also be deposited in inactive tissue such as nails, haris or the outer layer of skin.

Reference:
Kent, C. 1998. Basics of Toxicology. John Wiley & Sons, Inc. New York
http://en.wikipedia.org/wiki/Excretion

Phase II Reactions

What is phase II reactions?
What are types of phase II reactions? 

What is phase II reactions?
During phase II reactions, the toxic substances or its metabolite is bound with a compound that generally renders the newly synthesized molecule less toxic. This type of reaction is referred to as conjugation. Conjugation is the joining of two substances to form a single molecule, which can increase water solubility and excretion. One of the most important conjugation is conjugation with glucuronidation.

Metabolism

What is metabolism?
How does the toxicant biotransformed?
What are factors affecting metabolism?

What is metabolism?
Metabolism or often referred to biotransformation is a process which result in changing in the chemical structure of the toxic substance. These changes in a variety of tissue such as liver, kidney, lung, skin and GI tract as well. Primary spot for biotransformation is in liver.

Catabolic reaction (Phase I)

This include oxidation, reduction and hydrolisis.

Oxidation
It occurs when a molecule combines with oxygen, loses hydrogen, or loses one or more electrons.

Many toxicants are metabolized by the enzymes cytochrome P-450 reductase and cytochrome P-450 in association with NADPH (co-enzyme: nicotinamide adenine dinucleotide phophate). These enzymes are abundance in endoplasmic reticulum of liver cells for detoxification.

Distribution

What structure plays important role for distribution?
How circulatory system structured?
Is there any barrier for distribution?

What structure plays important role for distribution?
Absorption into and out to bloodstream occurs in the circulatory system which is the capillaries, inhaled toxicants diffuse accross the alveoli.

How circulatory system structured?
It is composed of the heart along with an extensive system of blood vessels that transport oxygen and nutrient-rich blood to the cells. The blood carries oxygen, waste products, nutrients and toxic substances into and out of the bloodstream by active and passive mechanisms.