9. environmental health and toxicology

ENVIRONMENTAL HEALTH AND TOXICOLOGY

Mrs. OFELIA SOLANO SALUDAR

Department of Natural SciencesUniversity of St. La Salle

Bacolod City

Focuses on external factors that cause disease, including elements of the natural, social, cultural, and technological worlds in which we live.

Rachel Carson’s Silent Spring in 1962 focused on the discharge, movement, fate, and effects of synthetic chemical toxins.

ENVIRONMENTAL HEALTH

HEALTH is a state of complete physical, mental, and social well-being, not merely the absence of disease or infirmity.

A DISEASE is an abnormal change in the body’s condition that impairs important psychological or functions. Diet and nutrition, infectious agents, toxic substances, genetics, trauma, and stress all play roles in morbidity (illness) and mortality (death).

THE GLOBAL DISEASE BURDEN

Is changing due to public health successes.

Smallpox was completely wiped out in 1977.

Polio has been eliminated everywhere in the world except for a few remote villages in northern Nigeria.

Epidemics of typhoid fever, cholera, and yellow fever are now rarely encountered.

AIDS has become a highly treatable disease.

According to the WHO, chronic diseases now account for nearly 60% of the 56.5 million total deaths worldwide each year and about half of the global disease burden.

Rising life expectancies is also due to declining child mortality.

Mortality data is now based on Disability adjusted life years (DALYs) as a measure of disease burden.

What changes

could you make in your

lifestyle to lessen your risks from

the diseases in this table? What would

have the greatest

impact on your future well-being?

Infectious and emergent diseases still kill millions of people.

A wide variety of pathogens afflict humans, including viruses, bacteria, protozoans, parasitic worms, and flukes. People rarely die from parasites, but they can be extremely debilitating, and can cause poverty that leads to other deadly diseases.

Diarrhea, acute respiratory illnesses, malaria, measles, tetanus, kill about 11 million children under age 5 every year in the developing world.

Better nutrition, clean water, improved sanitation, and inexpensive inoculations could eliminate most deaths.

Emergent diseases are those not previously known or that have been absent for at least 20 years. Rapid international travel makes it possible for these new diseases to spread around the world at jet speed.

Epidemiologists warn that the next deadly epidemic is only a plane ride away.

Emergent diseases in humans and ecological diseases in natural communities arise due to stresses in biological systems that upsets normal ecological relationships.

Of growing concern are adverse synergistic interactions between emerging diseases and other infectious and non-infectious conditions leading to the development of novel syndemics.

Many emergent diseases originated from a non-human animal species, e.g.:HIV originated in chimpanzees. SARS came from the Masked Palm Civet,

which is native to China.

SARS virus

AIDS- HIV

Ebola

Factors Contributing To Disease Emergence:

Microbial adaption; e.g. genetic drift and genetic shift in Influenza A

Changing human susceptibility; e.g. mass immunocompromisation with HIV/AIDS

Climate and weather; e.g. diseases with zoonotic vectors such as West Nile Disease (transmitted by mosquitoes) are moving further from the tropics as the climate warms.

Change in human demographics and trade; e.g. rapid travel enabled SARS to rapidly propagate around the globe

Economic development; e.g. use of antibiotics to increase meat yield of farmed cows leads to antibiotic resistance

Breakdown of public health; e.g. the current situation in Zimbabwe

Poverty and social inequality; e.g., tuberculosis is primarily a problem in low-income areas

War and famine Bioterrorism; e.g. 2001 Anthrax attacks Dam and irrigation system construction;

e.g. malaria and other mosquito borne diseases

ECOLOGICAL DISEASES Ebola hemorrhagic fever kills up to 90% of its human

victims. A global outbreak killed ¼ of all the gorillas. Chronic wasting disease (CWD) is caused by a prion.

CWD is one of a family of irreversible, degenerative neurological diseases known as transmissible spongiform encephalopathies (TSE) that include mad cow disease in cattle, scrapie in sheep, and Creutzfelt-Jacob disease in humans.

Tropical diseases, such as malaria, cholera, yellow fever, and dengue fever, have been moving into areas from which they were formerly absent as mosquitoes, rodents, and other vectors expand into new habitat.

CONSERVATION MEDICINE is an emerging discipline that attempts to understand how our environmental changes threaten our own health as well as that of the natural communities on which we depend for ecological services.

Resistance to drugs, antibiotics, pesticides is increasing.

How microbes acquire antibiotic

resistance. (a) Random

mutations make a few cells resistant.

When challenged by antibiotics, only

those cells survive to give rise to a

resistant colony. (b) Sexual reproduction

(conjugation) or plasmid transfer move genes from

one strain or species to another.

The protozoan parasite that causes malaria is now resistant to most drugs, while the mosquitoes that transmit it have developed resistance to many insecticides.

Antibiotic MisuseReasons for antibiotic resistance to develop: Antibiotics do not

work against certain diseases, e.g. viral infections.

Antibiotics are given when the person could recover fully without them.

Starting and not finishing a full prescription.

Widespread use of antibiotics in animal agriculture.

ECOTOXICOLOGY Study of toxins

(poisons) and their effects, particularly on living systems.

A broad field, drawing from biochemistry, histology, pathology, pharmacology, and many other disciplines.

Toxins are harmful even in extremely dilute concentrations. In some cases billionths, or even trillionths of a gram can cause irreversible damage.

Allergens are substances that activate the immune system. Widely used in plastics, wood

products, insulation, glue, and fabrics concentrations in indoor air can be much higher than in normal outdoor air.

Sick building syndrome: headaches, allergies, chronic fatigue, and other symptoms caused by poorly vented indoor air contaminated by mold spores, CO, nitrogen oxides, formaldehyde, and other toxins released from carpets, insulation, plastics, building materials, and other sources.

Immune System Depressants suppress the immune system. Dead animals

contained high levels of pesticide residues, polychlorinated biphenyls (PCBs), and other

contaminants that are suspected of disrupting the immune system and making it susceptible to a variety of opportunistic

infections.

Endocrine hormone disruptors interfere with the function of normal chemical messengers in the body.

Hormone mimics have similar shapes to natural hormones and amply their effects.

Hormone blockers prevent natural hormones from attaching to their target organ.

Endocrine disruption, linked to increased

risk of breast cancer, develop-

mental and reproductive

toxicity; allergies and

immuno-toxicity.

BPA is known to be a hormone mimic used for plastic products ranging from water bottles to

tooth-protecting sealants. The chemical can cause abnormal chromosome numbers which is the

leading cause of miscarriages and several forms of mental retardation. It also is an environmental estrogen and may alter sexual development in both males and females. Bills are considered to

ban BPA and certain phthalates in children’s toys and feeding products.

Use 1, 2, 4, 5 with your food! All the others are NOT good for you.

Neurotoxins specifically attack nerve cells and are both extremely toxic and fast-acting. Lead and mercury kill nerve cells and

cause permanent neurological damage. Anesthetics (ether, chloroform, halothane,

etc.) and chlorinated hydrocarbons (DDT, Dieldrin, Aldrin) disrupt nerve cell membranes necessary for nerve action.

Organophosphates (Malathion, Parathion) and carbamates (carbaryl, zeneb, maneb) inhibit the enzyme that regulates signal transmission between nerve cells and the tissues or organs they innervate.

These dozen chemicals may be

responsible for widespread

behavioral and cognitive

problems, but the scope of the

chemical dangers in our environment

is likely even greater!

Mutagens are agents, such as chemicals and radiation,

that damage or alter genetic material (DNA) in

cells. This can lead to birth defects if the damage occurs during embryonic or fetal growth, or trigger neoplastic (tumor) growth in adults.

When damage occurs in reproductive cells, the results can be passed on to future generations.

There is no “safe” threshold for exposure to mutagens. Any exposure has some possibility of causing damage.

Teratogens are chemicals that

cause birth defects in an unborn fetus: ethanol, benzene,

lead, mercury

Mercury can cause sensory impairment, lack of coordination, and disrupt other nervous

system functions. Lead, another neurotoxin, was used as an additive in gasoline until

1976. Following a ban of its use, an 80% drop in

blood lead levels were observed, as well as a 6-point gain in the average IQ of children.

Bioaccumu-lation and biomag-nification increase concen-

trations of toxins.

Biomagnification occurs when the toxic burden of a large number of organisms at a lower trophic level is accumulated and concentrated by a predator in a higher

trophic level.

PERSISTENT ORGANIC POLLUTANTS (POPS) often accumulate in food webs and reach toxic concentrations in long-living top predators such as humans, sharks, raptors, swordfish, and bears. Polybrominated diphenyl ethers

(PBDE) are used as flame-retardants in textiles, foam in upholstery, and plastic in appliances and computers.

Relatively low exposures in the womb or shortly after birth can irreparably harm children’s reproductive and nervous systems.

Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA, also known as C8) are used to make nonstick, waterproof, and stain-resistant products such as Teflon, Gortex, Scotchguard, and Stainmaster.

This chemical family has been shown to cause liver damage as well as various cancers and reproductive and developmental problems in rats.

Exposure may be especially dangerous to women and girls, who may be 100x more sensitive than men to these chemicals.

Phthalates are found in cosmetics, deodorants, and plastics (e.g. soft polyvinyl chloride or PVC) used for food packaging, children’s toys, and medical devices. Some cause kidney and liver damage and possibly some cancers.

Many phthalates act as endocrine hormone disrupters, and have been linked to reproductive abnormalities and decreased fertility.

Perchlorate is a waterborne contaminant left over from propellants and rocket fuels. Polluted water used to irrigate crops has introduced the chemical into the human food chain. Perchlorate can interfere with iodine uptake in the thyroid gland, disrupting adult metabolism and childhood development.

Chemical interactions can increase toxicity

Antagonistic reactions of some materials interfere with the effects or stimulate the breakdown of other chemicals. Ex.: Vitamins E and A can reduce the response to some carcinogens. Other materials are additive when they occur together in exposures. Rats exposed to both lead and arsenic show 2x the toxicity of only one of these elements.

Synergism is an interaction in which one substance exacerbates the effects of another. Ex.: occupational asbestos exposure or smoking increases lung cancer rates 20-fold. Asbestos workers who also smoke, however, have a 400-fold increase in cancer rates.

How many other toxic chemicals are we exposed to that are below threshold limits individually but combine to give toxic results?

Factors Influencing Toxicity There are many individual genetic

differences in sensitivities. Chemicals with a high level of persistence

that do not degrade easily are more likely to cause long-term effects.

The solubility of a substance; whether it can dissolve in oil or water.

Water-soluble toxins tend to be passed through the body via the kidneys fairly easily.

Oil-soluble toxins, once ingested, can pass directly into cells and tissues, allowing them to accumulate.

MEASURING TOXICITY“The dose makes the poison”

How a material is delivered, at what rate, through which route of entry, and in what medium determine toxicity.

It matters not only what is there, but how much, where it is located, how accessible it is, and who is exposed. At some level, the mere presence of a substance is insignificant.

There are different levels of toxicity, and there are different degrees of carcinogenicity, mutagenicity, and teratogenicity.

For example, Ricin, a protein found in castor bean seeds is so toxic that 0.3 billionths of a gram given intravenously will generally kill a mouse.

On the other hand, saccharin is a suspected carcinogen whose effects may be vanishingly small.

The question is: Should we set pollution levels that will protect everyone, including the most sensitive people, or

only aim to protect the average person?

A convenient way to describe toxicity of a chemical is to determine the dose to which 50 % of the test population is

sensitive. In the case of a lethal dose, this is called the LD50.

Substance LD50 (mg/kg)

Table sugar 29,700

Monosodium Glutamate (MSG) 16,600

Vitamin C 11,900

Alcohol (Ethanol) 7,060

Table salt 3,000

Aspirin 200

Caffeine 192

Nicotine 50

Capsaicin (active component of chili peppers)

47.2

Poison Dart Frog Toxin 0.002

Polonium-210 (Nuclear Waste) 0.000000001

Exposure and susceptibility to toxins determine

how we respond to them

RISK ASSESSMENT AND ACCEPTANCE Risk is the possibility of suffering harm or loss. Risk assessment is the scientific process of

estimating the threat that particular hazards pose to human health. This process includes risk identification, dose response assessment, exposure appraisal, and risk characterization.

Exposure assessment is the estimation or determination of the magnitude, frequency, duration, and route of exposure to a possible toxin.

Risk management combines principles of environmental health and toxicology together with regulatory decisions based on socioeconomic, technical, and political considerations.

Although each individual stress may not be life-threatening, the cumulative effects of all the environmental stresses, both natural and human-caused, to which we are exposed may seriously shorten or restrict our lives.

Should we demand that pollution be reduced to zero if possible, or as low as is technologically feasible?

In setting standards for environmental toxins, we consider: (1) combined effects of exposure to many different sources of damage, (2) different sensitivities of members of the population, and (3) effects of chronic as well as acute exposures.

What risks are generally considered

acceptable? High probability of

exposure with low severity.

Mercury in seafood.

Low probability of exposure with high severity.

Nuclear power plants.

Public policy decisions are made based on risk

assessment and promoting the best

health possible in the population.

Examples of labels that have been required or proposed as a result of public health concerns.

Environmental Impact of IndustriesIndustr

yAir Water Land Human

Petrochemical

noxious and toxic emissions from refining, processing plants

factory emissions to water bodies

landfill disposal of waste solids & sludge; accidental spills during transport & storage

toxicity and disruption of lifestyle

Metal particulate, gas emissions during forging, working, fabrication

discharge of pickling liquors & other waste disposal; heavy metals

slag, waste products from processing

toxicity

Mining particulates from surface mining & transportation; noxious & toxic fumes from smelting

runoff from mines and waste disposal

dumping of tailings & processed wastes; disruption of agriculture, forestry, recreation

heavy metals, particulates

Environmental Impact of IndustriesIndustr

yAir Water Land Human

Food noxious fumes from food processing

sewage with high organic content

uncomposted organics and other wastes to landfill

toxicity and allergens

Agri-culture

drift of agricultural chemicals (pesticides, herbicides, fungicides, fertilizers), pollen, & dust

runoff of agrochemicals to surface waters; percolation to groundwater; silting of water

erosion, depletion of organic material & organisms

toxicity of chemical; loss of soil

Pulp & Paper Industry

noxious fumes

emissions of mercury, chlorines, organics; silt from deforestation; loss of habitat

destruction of habitat by clear-cutting; erosion

mercury contamina-ted seafood

Product Waste Materials

Plastics organic chlorine compounds, organic solvents

Pesticides organic chlorine compounds, organic phosphate compounds

Medicines organic solvents and residues, heavy metals

Paints heavy metals, pigments, solvents, organic residues

Petroleum products

oil, phenols, organic compounds, heavy metals, ammonia, salt acids, caustics

Metals heavy metals, fluorides, cyanides, acid and alkaline cleaners, solvents, pigments, abrasives, plating salts, oils, phenols

Leather heavy metals, organic solvents

Textiles heavy metals, dyes, organic chlorine, compounds, solvents

Wastes Generated From Manufacture Of Common Products

“Do you want to stop reading

those ingredients while we’re

trying to eat?”