Environmental Impact and Health Effects of Hydrogen

Hydrogen, the first element in the periodic table, is a colorless, odorless and insipid gas, formed by its diatomic molecules, in normal conditions. The hydrogen atom is formed by a nucleus with one unit of positive charge and one electron. It’s one of the main compounds of water and of all organic matter, and it’s widely spread not only in the Earth but also in the entire Universe. There are three hydrogen isotopes: protium, mass 1, found in more than 99,985% of the natural element; deuterium, mass 2, found in nature in 0.015% approximately, and tritium, mass 3, which appears in small quantities in nature, but can be artificially produced by various nuclear reactions.

Hydrogen forms 0.15 % of the earth's crust and it is the major constituent of water. 0.5 ppm of hydrogen H2 and variable proportions as water vapor are present in the atmosphere. Hydrogen is also a major component of biomass, constituting the 14% by weight. Hydrogen occurs naturally in the atmosphere. The gas will be dissipated rapidly in well-ventilated areas. Any Effect of hydrogen on plants or animals would be related to oxygen deficient environments. No adverse effect is anticipated to occur to plant life, except for frost produced in the presence of rapidly expanding gases. No evidence is currently available on the effect of hydrogen on aquatic life.

Hydrogen is the most flammable of all the known substances. It is slightly more soluble in organic solvents than in water. Many metals absorb hydrogen. Hydrogen absorption by steel can result in brittle steel, which leads to faults in the chemical process equipments. At normal temperature hydrogen is a not very reactive substance, unless it has been activated somehow; for instance, by an appropriate catalyser. At high temperatures it’s highly reactive. Although in general it’s diatomic, molecular hydrogen dissociates into free atoms at high temperatures. Atomic hydrogen is a powerful reductive agent, even at ambient temperature. It reacts with the oxides and chlorides of many metals to produce free metals. It reduces some salts to their metallic state and reacts with a number of elements, both metals and non-metals to produce their hydrides. Atomic hydrogen reacts with organic compounds to form a complex mixture of products. The heat released when the hydrogen atoms recombine to form the hydrogen molecules is used to obtain high temperatures in atomic hydrogen welding.


The most important use of hydrogen is the synthesis of ammonia. The use of hydrogen is extending quickly in fuel refinement, like the breaking down by hydrogen (hydrocracking), and in sulphur elimination. Huge quantities of hydrogen are consumed in the catalytic hydrogenation of unsaturated vegetable oils to obtain solid fat. Hydrogenation is used in the manufacture of organic chemical products. Huge quantities of hydrogen are used as rocket fuels, in combination with oxygen or flour, and as a rocket propellant propelled by nuclear energy. Hydrogen can be burned in internal combustion engines. Hydrogen fuel cells are being looked into as a way to provide power and research is being conducted on hydrogen as a possible major future fuel. For instance it can be converted to and from electricity from bio-fuels, from and into natural gas and diesel fuel, theoretically with no emissions of either CO2 or toxic chemicals.



As hydrogen is extremely flammable, its many reactions may cause fire or explosion. As the gas mixes well with air, explosive mixtures are easily formed. Moreover the gas is lighter than air. The gas can be absorbed into the body by inhalation and high concentrations can cause an oxygen-deficient environment. Individuals breathing such an atmosphere may experience symptoms which include headaches, ringing in ears, dizziness, drowsiness, unconsciousness, nausea, vomiting and depression of all the senses. The skin of a victim may have a blue color. Under some circumstances, death may occur. Hydrogen is not expected to cause mutagenicity, embryotoxicity, teratogenicity or reproductive toxicity. Pre-existing respiratory conditions may be aggravated by overexposure to hydrogen. When inhaled a harmful concentration of this gas in the air will be reached very quickly.

Heating may cause violent combustion or explosion as the gas reacts violently with air, oxygen, halogens and strong oxidants causing fire and explosion hazard. Metal catalysts greatly enhance these reactions. High concentrations in the air cause a deficiency of oxygen with the risk of unconsciousness or death. We must check oxygen content before entering a suspected area as there is no odor warning if toxic concentrations are present. We may measure hydrogen concentrations with suitable gas detector (a normal flammable gas detector is not suited for the purpose). In case of inhalation problem we should shut off its supply. In case it not possible and there seems no risk to surroundings, let the fire burn itself out; in other cases extinguish with water spray, powder, carbon dioxide. In case of fire we should keep its cylinder cool by spraying with water. One must combat fire from a sheltered position and rush for medical aid and advice in case of all inhalation and contact cases.