By EDUARDO GONZALES, MD.
Q: A recent headline of a national daily said that mercury levels are rising in Philippine waters and mine sites. Why is mercury a big concern?—firstname.lastname@example.org
A: At least five bodies of water in Luzon and Mindanao and several mining sites all over the country have rising levels of mercury, according to the Philippine Minamata Initial Assessment (MIA) report, which studied the prevalence of mercury in our country.
The bodies of water and sites suspected to have high concentrations of mercury include Manila Bay in Metro Manila, Meycauayan River in Bulacan, Mambulao Bay in Camarines Norte, Lumanggang Creek, and Naboc River, both in Davao region, the abandoned Palawan Quicksilver Mines in Puerto Princesa City, Mabuhay Vinyl Corp. in Iligan City, a chlor-alkali producer, and mining and gold processing sites in Camarines Norte and Masbate.
Mercury, or “asoge,” in Filipino, is a naturally occurring heavy metal that is of great concern because it is toxic. Experts say there is no safe level of mercury in humans and the World Health Organization (WHO) considers mercury as one of top 10 chemicals of major public health concern.
MERCURY USE IN THE PHILIPPINES
Before its harmful effects became widely understood, mercury was extensively employed for medical purposes. It used to be a component of many medical diagnostic equipment including blood pressure apparatuses and clinical thermometers, some drugs, and antiseptic agents—remember mercurochrome, a topical antiseptic used for minor cuts and abrasions?
Mercury is no longer used in the medical and dental fields in the Philippines. Mercury-containing equipment were phased out from medical facilities in the country in 2010 in compliance with a Department of Health (DOH) directive. Mercury, however, is still widely used, in its inorganic and organic forms in many industries.
TOXIC EFFECTS OF MERCURY
Elemental mercury, the form of inorganic mercury that was used in clinical thermometers, is harmless if touched or swallowed. It is so thick and slippery that it falls off the skin or egested by our digestive tract without being absorbed. When made airborne into small droplets and inhaled, as when spilled mercury is vacuumed up from the floor, health problems can arise. Inhaled elemental mercury can cause vomiting, difficulty of breathing, cough, metallic taste, and bleeding and swollen gums. Depending on the amount of mercury inhaled, permanent lung damage and death can occur.
Organic mercury, on the other hand, as exemplified by methyl mercury, the form of the metal that is found in our bodies of water, is dangerous when breathed in, eaten, or absorbed through the skin, for long periods of time. It results in gradual damage to the lungs, kidney, and brain that manifests as difficulty of breathing, kidney failure, numbness and pain in certain parts of the skin, uncontrollable shaking or tremor, inability to walk well or to swallow, blindness and double vision, memory problems, seizures, and death. In fetuses (in wombs of mothers with high blood level of mercury), infants, and children, it impairs brain development.
According to the MIA, methyl mercury in our waters comes from landfills, waste water treatment, coal burning power plants (coal contains mercury as a natural contaminant), and metal production.
Methyl mercury in our waters is absorbed by algae, the staple food of small fish that scavenge near shorelines. The level of mercury among fish gets higher as one goes up the food chain because small fish are eaten by larger fish which, in turn, serve as prey for still larger fish.
In short, we can get mercury poisoning when we consume mercury-contaminated fish.
Fortunately, at present, most of our saltwater and freshwater fish contain only minute levels of mercury, which means mercury contamination of our waters is not a serious problem yet, but unless a comprehensive regulatory system for mercury, from its acquisition to its disposal, is put in place, it might soon be.
In any case, there are large fish such as sharks, tilefish, swordfish, and king mackerels that sometimes already contain dangerously high levels of mercury in their tissues. We should consume these fish in moderation.