Chapter Ii -Medical Biology - Course Content Ecology 2023-2024 PDF

Exercise 2. Topic: The home environment and food as a source of pathogenic agents for humans. Glossary: Aetiological pathogenic aagent/factor-a chemical, biological or physical entity that may cause disease in the human body. Building-Related illnesses (BRIs).Disorders caused by pathogenic factors /...

Exercise 2. Topic: The home environment and food as a source of pathogenic agents for humans. Glossary: Aetiological pathogenic aagent/factor-a chemical, biological or physical entity that may cause disease in the human body. Building-Related illnesses (BRIs).Disorders caused by pathogenic factors / pollutants coming directly from the internal environment of the building,and diagnosed as directly attributed to pathogenic factors in the building. Cosmopolitan species - species with a wide geographical coverage occurring on different continents and in different climates. Dermatophytes - fungi with the ability to break down keratin and grow in the stratum corneum of the epidermis, in hair and nails; they may cause infections of smooth and hairy skin, hair and nails. Facultative parasite - do not rely on the host in order to complete its life cycle; can survive without the host, and only sometimes perform parasitic activities. Obligate parasite -a parasitic organism thich can’t survive without the host organism, cannot complete its life-cycle without exploiting a suitable host and it is characterized by a high degree of specialization. Incubation period- a period between exposure to a pathogenic organism, a chemical, or radiation, and appearance of the first symptoms and signs. Sick Building Syndrome (SBS) –the group of sick syndroms (manifesting themselves in few minutes to hours ), when the person leaves the building; strictly related to staying in a internal environment of the building.The occurrence of syndromes is mainly related to the insufficient amount of fresh air in the room and its poor quality (pollutants) Threshold limit value (TLV) of a chemical substanceor physical agents - the time-weighted average concentration of a toxic substance over a normal 8-h workday and 40-h workweek, to which nearly all workers may be repeatedly exposed, every day, without adverse health effects; also absolute exposure limit that should not be exceeded at any time. Aetiological factors of invasive diseases related to the home as the environment of human life A house is a specific human habitat, in which an individual spends a significant part of each day. According to the research conducted in the United States, people spend approximately 87% of a day (24h) in indoor environments (at home, school, work, shops, restaurants, etc.) and additionally about 6% of a day in a vehicle. In the indoor environment (conventionally known as the "home") each of us, as an inhabitant, is affected by specific biotic and abiotic factors that may pose a threat, however, at the same time we are partially protected from an adverse impact of the external environment. Unfavourable abiotic factors of the external environment include temperature, moisture, solar radiation, noise, dusts and chemical pollution of air, while among biotic factors there are predacious, poisonous and parasitic animals and also microbe-vectors, poisonous plants, pathogenic bacteria and fungi. In the "home" environment, there is an inter-individual transmission of pathogens - direct (droplet path, direct human-human or human-animal contact) or indirect (dusts carrying pathogens, common items, sanitary utensils, etc.). Specific hazards in confined spaces may include:  pathogenic bacteria (e.g. Legionella sp., Pseudomonas aeruginosa from air-conditioning devices),  fungi,  house dust mites and other mites (e.g. Dermatophagoides sp., Sarcoptes sp.)  insects (flies, fleas, bedbugs, lice, prussians),  fur and epidermis of animals and humans,  chemical compounds - oxidation products arising in heating-units, cookers and also while smoking tobacco: carbon monoxide, carbon dioxide, nitrogen oxides, aromatic hydrocarbons, - volatile and semi-volatile organic compounds produced by refrigerating units, i.e. formaldehyde, benzene, acetone, chloroform, aliphatic and aromatic hydrocarbons - insecticides, polychlorobiphenyles from furniture, paints, clothing materials (a lack of an adequate room ventilation system) and also from food, - terpens (limonene, pinen) derived from plants, - lead components that used to be added to paintsin the past, - asbestos fibres used in building materialsin the past,  noxious radiation of radon, radium and uranium, which can be found in plasters, and walls of houses.  injuries of extremities, burns of body surface, intoxications as the result of mechanical and chemical damages or electrocution. Each building is characterized by its flora and fauna which may be pathogenic to its inhabitants. Living pathogenic bacteria(e.g. Pseudomonas aeruginosa, Vibrio cholerae, staphylococcal bacteria, Klebsiella sp.) existing in the form of biofilms may be found on household equipment (e.g. heat exchangers, utensils, flower-vases) as well as on hospital equipment (tubes, catheters, containers).Bacteria and/or fungi in biofilms exhibit increased resistance to chemical agents, which is conditioned by the production of a protective extracellular substance and enzymes, as well as mutual protectionist interactions (transmission of stimuli to reproduction and microcolonies formation, feeding with useless metabolites of other species, etc.) Diseases associated with staying in buildings In the last decades, on the basis of a causal relationship of disease symptoms, two types of health problems have been established. They are associated with the conditions prevailing in non-industrial (residential and office) buildings: 1. Sick Building Syndrome (SBS); 2. Building-Related Illnesses (BRIs). The occurrence of complaints related to poor air quality reported by people staying indoors, resulted in coining of the term "sick building syndrome" (SBS)(WHO, 1987).A building can be called sick if "20% of users state that a building is the cause of the symptoms of malaise, i.e. that the symptoms appear and intensify only while in the building, and disappear almost immediately after leaving the building." SBS has been defined as a set of symptoms of physical and mental discomfort that are so unspecific that they cannot be associated with any specific factor. Symptoms related to staying indoors include: - dryness and irritation of the mucous membranes of the eyes, - dryness and irritation of the throat, dry cough, occluded nose, pain in the sinus area, - dryness and irritation of the skin, exfoliation of the epidermis, - headache and dizziness, drowsiness, dejection, impairedconcentration, - nausea, heartburn, - chest pain, breathing difficulties, - exacerbation of ailments related to an existing disease, e. g. asthma. The above symptoms result from limited air exchange in rooms, presence of chemical agents - emission of organic and inorganic pollutants (combustion products, solvents, adhesives, chlorine compounds, etc.), biological contaminants (mites, insects, fungi, bacteria, plant pollen, etc.) and presence of pets, as well as noise and vibration, radiative phenomena, including ionization of air due to radioactive radiation and electrostatic phenomena, operation of the electromagnetic field (PEM). There are no clinical tests available to establish the diagnosis of SBS, it is rather recognized by identification of indoor air quality (IAQ) environmental problems or higher combined symptom rates among a group of a building occupants. The following observations are important in the diagnosis of SBS: - immediate resolution or reduction of symptoms after leaving the building, - seasonality of ailments (overheating, hypothermia), - the occurrence of similar symptoms in individuals sharing the same flat or office. Where there is a proven link between disease symptoms and causative factors directly related to building contaminants, the disorder is classified as building-related illness (BRI). BRIs are less common than SBS and by definition are more serious in prognosis than mere discomfort. The BRIs include: - diseases caused by toxic factors (carbon monoxide poisoning, exposure to radon - lung cancer), - infectious diseases (Legionnaires' disease, Pontiac fever, humidifier fever), - allergic diseases (asthma, hay fever, hypersensitivity pneumonitis). Medical diagnosis based on clinical investigation of symptoms is the usual methodfor recognizing BRIs. In the case of BRIs there can be a long latency (asymptomatic) period.Building-related illnesses generally require a prolonged recovery time or may become a chronic problem for a patient, even when they are no longer exposed to the aetiological factor. Chemical factors occurring in the home environment Carbon monoxide (CO) Among the numerous chemical pollutants, carbon monoxide threatens not only health but even life of people staying in residential areas. Carbon monoxide, colloquially known as flue gas, is a colourless and odourless, highly poisonous gas, slightly lighter than air, with an affinity forhaemoglobin that is about 250 times greater than oxygen. It forms carboxyhaemoglobin, in which the combination of carbon monoxide and haemoglobin is more stable than the combination of oxygen and haemoglobin in oxyhaemoglobin. It leads to tissue hypoxia, which in turn can lead to death. Inhalation of air with a concentration of 0.16% volumetricCO causes death after two hours. Carbon monoxide is formed as a result of incomplete combustion of many fuels (wood, oil, gas, petrol, kerosene, propane, coal) caused by the lack of adequate amount of oxygen. The lack of fresh (external) air supply to the device in which combustion occurs, contamination, destruction or incorrect adjustment of the gas burner, also premature closing of a furnace hearth or cooker is particularly dangerous in apartments with windows tightly closed or sealed for the winter. Radon (Rn) The harmful contaminants naturally present in rooms are radon ( 222Rn) and the products of its decay. Radon is a naturally occurring, colourless and odourless noble gas; it is formed as a result of radioactive decay of radium (226Ra). It is not radon itself, but the products of its decay that are the source of high-energy alpha radiation which can be harmful to health of room inhabitants. Additionally, these products are solid heavy metals that can combine with the aerosol particles present in the internal air and that can be introduced into the human lungs when breathing. Radon from the ground can penetrate into basements of buildings through gaps in floors or walls and installation leaks and get into rooms together with natural gas and running water. In addition, as a result of the chimney effect (floating heated air), it is sucked from basements to upper floors of buildings. Construction materials from which walls and ceilings of a building are made as well as the type of finishing materials are of great importance for the degree of air pollution in flats. All raw materials of industrial origin are particularly radioactive: volatile ash, slag, phosphogypsum and concrete. The average radium concentration in building materials is around 100 Bq/kg. Radon and the products of its decay are inhaled by humans together with the atmospheric air, which is why the lungs are the organs most exposed to their impact. The effects can be manifested after years in the form of lung cancer and even leukaemia. According to the International Radiological Commission, long-term exposure to indoor radon of 100 Bq/m3 increases the risk of lung cancer. Asbestos Asbestos is a naturally occurring fibrous silicate mineral. It is constructed as a long, thin, fibrous crystals that can be released into the atmosphere by abrasion and other processes. Exposure to asbestos (inhalation route) causes asbestosis: pleural effusions, pleural plaques, pleuritic, diffuse pleural thickening. It can also cause lung and laryngeal cancer, as well as mesothelioma (a type of cancer almost exclusively caused by asbestos exposure) and chronic obstructive pulmonary disease (COPD). There is no specific amount of asbestos to which exposure would be safe, but it generally has the worst effects when a person is exposed to an intense concentration of it, or is exposed on a regular basis over a long period. Asbestos-related diseases have a long latency period, often taking decades to develop, thus the majority of patients with asbestos-related diseases are men in their 60s or older. The damages it causes are not reversible. Asbestos is on the list of substances with a proven carcinogenic effect under occupational exposure conditions, therefore, there are recommendations to keep its concentration in the air as low as possible. The threshold limit value (TLV) of 0.1 fibers per cubic centimeter (f/cc) [only asbestos fibers meeting certain criteria (e.g., length) will be counted, the weight of fibers is not the criterium]. Since 1999, the use of asbestos (eternit) has been banned in Poland, however, this material is still present in many houses and whena façade and roofing are destroyed, it is gradually released into the environment. Ozone In most households, devices such as photocopiers, scanners and printers have recently been used increasingly. They emit harmful chemicals, e.g. ozone, nitrogen oxides: NO and NO2. It may cause adverse health effects, especially in people who are exposed to the substances when working in poorly ventilated rooms. The main way of absorbing ozone by the human body is via the respiratory system. TLV for ozone is:0.05 ppm (0.10 mg/m³) -heavy work, 0.08 ppm (0.16 mg/m³) -moderate work,0.10 ppm (0.20 mg/m³) – light work. The first symptoms of short-term exposure to ozone are irritation of the throat and cough, as well as irritation of the conjunctivae. Long-term effects of low ozone concentrations can lead to irreversible, extensive changes in the lungs. The symptoms of acute poisoning,lung oedema (and even death), often do not become manifest until a few hours have passed and they are aggravated by physical effort. In the case of chronic exposure to ozone, the observed symptoms are eye irritation and tearing, visual deterioration, headache and dizziness, shortness of breath, nausea and decreased concentration. BIOLOGICAL FACTORS Microscopic fungi In the home environment (humid rooms), fungi from the genera Penicillium, Aspergillus, Cladosporium, Alternaria(producing a lot of spores that are released into the air –topic 5) as well as dermatophytes are common. Dermatophytes are fungi that have the ability to break down keratin (keratinolytic enzymes play a major role in its decomposition) and grow in the stratum corneum of the epidermis, in the hair and nails; they may cause infections of smooth and hairy skin, hair and nails. About 40 species of fungi representing the group of dermatophytes are recognized. The most important genera of dermatophytes are Microsporum, Trichophyton and Epidermophyton. In the dermatophytes classification, ecological criteria are often applied dividing dermatophytes, based on the source of their origin, into three groups: anthropophilic, zoophilic and geophilic (Figure 1). Division of dermatophytes based on the source of infection anthropophilic (isolated from humans, having the ability to cause infection, most frequently in human-human contacts) e.g. Trichophyton rubrum zoophilic (occurring in animals, having the ability to cause infection in animalhuman contacts) e.g. Microsporum canis geophilic (developing in the lithosphere, having the ability to cause infection in humans after contact with soil) e.g. Microsporum gypseum Figure 1. Types of dermatophytes depending on the source of infection. People may get infected with dermatophytes by: - contact with infected persons - anthropophilic species develop in the human body in asexual forms (anamorphic stage); their transmission takes place during direct or indirect (e.g. through combs, hair brushes, hats, bed linen, towels, carpets, etc.) contact between infected and healthy individuals; - contact with infected animals - natural reservoirs of zoophilic species are breeding or wild animals; - contact with contaminated soil - geophilic species usually occur in soil in which organic matter containing human and animal keratin is found; they can be a source of not only infection in humans and animals, but also in small rodents that play an important role in the transmission of the fungus between various species of mammals. Factors favouring dermatophyte infections: geographical and climatic conditions (seasonality of infections), excessive population density, poor hygiene of rooms, use of common sanitary and sport facilities, wearing plastic footwear and socks, poor personal hygiene (especially of feet), disturbances in the homeostasis of the host organism: - congenital or acquired immunodeficiencies, - endocrinopathies (adrenal, thyroid, parathyroid insufficiency), - allergic diseases of the atopic origin, - genetic factors (e.g. disorders in the construction of keratin), properties of the fungal strain: - virulence of the strain, including adherence capacity and proteolytic enzymes activity. Dermatomycoses Dermatophytes cause dermatomycoses termed tinea with the following Latin word for the part of the body affected by the disease process. Types of dermatomycoses: - Tinea capitis - mycosis of the scalp - Tinea barbae - mycosis of the beard - Tinea corporis, Tinea cutis glabrae - mycosis of the smooth skin - Tinea inquinalis - mycosis of the groins - Tinea manus, manuum - mycosis of hands - Tinea pedis, pedum - mycosis of feet - Tinea unguis, unguium - nail fungus Examples of aetiological agents that cause dermatomycoses in humans: Microsporum canis causes infections of the hairy scalp and torso; Epidemophyton floccosum causes mycoses of the smooth skin – interdigital mycosis, athlete’s foot; Trichophyton rubrum causes Tinea barbae. House dust mites There may be numerous mites in the home environment. Allergists distinguish two groups of mites: house dust mites(Dermatophagoides pteronyssinus, Dermatophagoides farinae, Euroglyphus maynei) present in dust, rugs, blankets, etc. andstorage mites (Acarus siro) found in various flour products. Two species of house dust mites: D. pteronyssinus and D. farinae are the main sources of allergenic proteins (allergens present in mite droppings) that cause allergic diseases in humans, such as chronic rhinitis, bronchial asthma and atopic dermatitis. Optimal conditions for the development of these species are ensured by high relative humidity (80%) and air temperature (about 25°C). The mites die at >55°C; dry cleaning kills adults, but does not reduce the allergen concentration. It is estimated that approximately 2 μg of allergenic proteins (Der p. 1 protein) in 1 g of dust is enough to cause hypersensitivity to dust mite allergens. At exposure >10 μg Der p.1 in 1 g of dust the risk of developing bronchial asthma increasessignificantly. Parasite species which may cause family and environmental invasions(discussed in practical exercises) Trichomonas tenax- oral trichomonas A cosmopolitan parasite of the oral cavity. Infection in immunologically competent people is asymptomatic. Trichomonosis/ trichomoniasis of the oral cavity can be manifested by dryness, taste disorders, burning and, rarely,spontaneous pain when swallowing. There may be inflammatory foci in the mucous membrane, inflammation of the tongue, pathological pockets (altered gingival pockets). In immunocompromised patients (elderly people, patients with cancer or alcoholics), cases of trichomonosis with inflammation affecting the organs such as the bronchi, lungs, salivary glands and even the liver and mammary glands were noted. It occurs only in trophozoite form; it does not form cysts. Transmission is direct from one person to another by kissing, or indirect by sharing eating utensils. Entamoeba gingivalis A protozoan (amoeba) with unconfirmed pathogenicity, occurring in the human oral cavity (in the interdental spaces, inside the gingival pockets and on the tonsils) in the trophozoite form (it does not form cysts). However, it is more frequently detected in people with oral mucosa lesions, inflammation of the paranasal sinuses or palatine tonsils. Transmission is direct from one person to another by kissing, or indirect by sharing eating utensils. Enterobius vermicularis - pinworm It is a cosmopolitan roundworm,monoxenous parasite of human large intestine.Pinworm infection (enterobiosis/ enterobiasis) is the most common type of parasitosis in the developed world. Those most likely to be infected with pinworm are children, people who take care of infected children and people who are institutionalized. In these groups, the prevalence can reach 50%. The disease is spread directly or indirectly. A person may be infected by swallowing (generally) or inhaling eggs. These eggs are deposited by adult females, measuring about 6 to 13 millimeters in length, around the anus. The eggs are translucent, ovoid and asymmetric (flattened on one side) with a thick shell (3 layers) and are coated with a sticky substance that dries up quite quickly, which allows them to float with the air movement. Pinworm eggs can survive in the indoor environment for 2 - 3 weeks. They can be embryonated or contain developed larvae. Modes of transmission include exposure to eggs in the environment (contaminated hands, toys, bedding, clothing, toilet seats),inhalation route (through dust), exogenous autoinfection (children carrying eggs into their mouths with their hands, after scratching around the anus), retroinfection (the migration of newly hatched larvae from the anal skin back into the rectum). Symptoms of enterobiosis include pruritus of the anus, loss of appetite, loss of body weight, pallor, restlessness and weakness, sleeping disorders (insomnia, nightmares) and nerve excitability. A diagnosis can be made by finding eggs in material from perianal skin folds [the cellulose-tape slide preparation (Graham, 1941) or the cellophane swab (NIH method)]. Demodex spp. – eyelash mite Of more than 100 different species cathegorized as the genus Demodex, only two parasites are found in humans - D. folliculorum and D. brevis. They are ectoparasites that live in regions of the skin with a lot of sebaceous glands (the nose, cheeks, forehead, beard), in hair follicles; also occur in the external auditory canal, on the skin of the chest or in the genital area. With a small population of the parasite, the demodecosis is asymptomatic. In the oligosymptomatic form,there appear skin lesions, such as pruritus, eczema, periodic purulent pustules, red spots as well as eye irritation (tickling of eyelids).In symptomatic demodecosis the following signs may be observed: chronic face dermatitis, pustules and inflammatory papules, vasodilation, abscesses, itching of the skin on the cheeks, under the eyes and around the nose, chronic inflammation of the eyelids (blepharitis), conjunctivitis and increased loss of eyelashes and eyebrows. The parasites are assigned a role in the pathogenesis of frequent dermatological diseases resistant to treatment (e.g. rosacea, maculopapular pustular acne). Prevalence of D. folliculorum increases with age of the host and is the highest in people over the age of 60 years (in old age it reaches up to 90%); there is no evidence of invasion in newborns and young children. The mites are transmitted between people through contact with the hair, secretions of the sebaceous glands, as well as through shared makeup or pillows.. Mammalian sucking lice Lice are blood-sucking (hematophagic) parasitic insects which occur worldwide (cosmopolitan); areobligate ectoparasites. Their body about 2–3.5 mm in length. is small, wingless and flattened. Their limbs possess claws to grip hair shafts and clothing fibres; they move by crawling. There are three types of lice that live on different area of the human body Pediculus humanus capitis - head louse Pediculus humanus humanus - body louse, clothes louse Pthirus pubis - pubic louse, “crab” louse. Pediculus humanus - human louse Adult Pediculus lice can live up to 30 days on a person’s body. Females can lay up 7-10 eggs (nits) per day (during life time about 50-300 eggs).To live, adult lice need to feed on blood several times daily. Without blood meals, the louse will die within 1 to 2 days off the host. There are two subspecies of this insect (a genetic analysis did not find any differences between the two subspecies):  The head louse resides close to the scalp to maintain its body temperature. Infestation with head lice is most common among preschool- and elementary school-age children and their household members. Head lice infest the head and neck and attach their eggs (nits) to the base of the hair shaft. Getting head lice (pediculosis capitis)is not related to cleanliness of the person or his or her environment. The most common way to get head lice is by direct head-to-head (hair-to-hair) contact with a person who already has head lice. Uncommonly, transmission may occur by: - wearing clothing (such as hats, scarves, coats, sports uniforms, or hair ribbons) worn by an infested person; - using infested combs, brushes or towels; - lying on a bed, couch, pillow, carpet, or stuffed animal that has recently been in contact with an infested person. Head lice survive less than 1– 2 days if they fall off a person and cannot feed; nits cannot hatch and usually die within a week if they are not kept at the same temperature as that found close to the scalp. Lousiness can be asymptomatic, particularly with a first infestation or when an infestation is light. The head louse mainly parasitizes in the temporal and occipital region pricking the skin and causes pruritus, scratching, bristles and scabs. Scalp itching (“pruritus”) is the most common symptom of its infestation and is caused by an allergic reaction to louse bites. Other symptoms may include a tickling feeling or a sensation of something moving in the hair, irritability and sleeplessness. Lice move quickly; nits are brown or white (empty shells) and attached to the hair.  The body louse live and lay eggs on clothing close to the skin and only move to the skin to feed. Body lice infestations (vagabond's disease, pediculosis vestimenti = pediculosis corporis) are spread most commonly by close person-to-person contact but are generally limited to persons who live under conditions of crowding and poor hygiene (for example, the homeless, refugees, etc.). In longstanding infections with the body louse the skin becomes roughened, thickened, and deeply bronzed by pigment Occasionally secondary bacterial infections (severe dermatitis) as a result of scratching (impetigo, infective dermatitis, furunculosis) can occur. For long time Pediculus humanus capitis was known as not able to transmit disease. Now there are evidences that both subspecies spread disease. They may be vectors of: louse-borne relapsing fever (Borrelia reccurentis), trench fever (Rickettsia quintana = Bartonella quintana) and epidemic typhus (Rickettsia prowazekii), and alsothey can be reservoirs of Toxoplasma gondii (experimentally proved for P. humanus corporis). Pthirus pubis - pubic louse, crab louse An insect is usually found on the pubic hair, however, it can also live in other areas of the body that are covered with coarse hair, such as the eyelashes (in children, eyelashes are the most common site of infestation – mainly by direct passage of the lice from their parents). It does not transmit aetiological factors of diseases; it irritates the skin, puncture sites are temporarily visible as blue spots. It may be the cause of blepharitis and conjunctivitis. Fleas - insects with a four-stadia life cycle consisting of eggs, larvae, pupae, and adults. There are many different fleaspeciesin the world; the most common are: cat fleas, dog fleas, human fleas and rat fleas. Pulex irritans – human flea A cosmopolitan flea species that has, despite of the common name, a wide host spectrum (various mammals, e.g. rats, cats, dogs, foxes), but prefers to feed on humans. Males and females feed on blood - pricks are troublesome, painful and can cause allergic reactions. Human flea is a vector for murine typhus (Rickettsia typhi), bubonic plague (Yersinia pestis), tularemia (Francisella tularensis), as well as Brucella abortus, Bacillus anthracis, Mycobacterium leprae, Rickettsia prowazekii, Salmonella spp. and Streptococcuspneumoniae. It can serve as an intermediate host for tapeworms: Dipylidium caninum, Hymenolepis nana, Hymenolepis diminuta. Cimex lectularis – bed bug A cosmopolitan species of insect, most frequently occuring in temperate and subtropical regions. It usually lives in flats and farm rooms. It feeds on the blood of humans and animals atnight. After pricking, it leaves red, itchy spots of irregular shape on the skin. The secretion of the fragrant glands can cause mucous membrane irritation and coughing. The transmission of pathogenic microorganisms by bed bug has not been confirmed. Food as a source of pathogenic factors for humans According to WHO (2020), contaminated food or water may cause foodborne illnesses which are usually infectious or toxic in nature and caused by bacteria, viruses, parasites or chemical substances. There are more than 200 such diseases – ranging from diarrhoea to cancers.Children under 5 years of age are particularly at risk of foodborne diseases Food can become contaminated at any point of production and distribution, and the primary responsibility lies with food producers. However, a large proportion of foodborne illness cases are caused by improperly prepared or improperly stored food at home, in outlets or at markets. From chemicals, of most concern for health are naturally occurring toxins and environmental pollutants.  Naturally occurring toxins include mycotoxins, toxins occurring in poisonous mushrooms, marine biotoxins, plants` cyanogenic glycosides. A long-term exposure can affect the immune system and normal development, or cause cancer.  Persistent organic pollutants (POPs) are compounds resistant to environmental degradation through chemical, biological, and photolytic processes; they persist for long periods of time in the environment, can accumulate and pass from one species to the next through the food chain.. Known examples are dioxins and polychlorinated biphenyls (PCBs), which are unwanted by-products of industrial processes and waste incineration. Dioxins are highly toxic and can cause reproductive and developmental problems, damage the immune system, interfere with hormones and cause cancer.  Heavy metals such as lead, cadmium and mercury are toxic.Food contamination with heavy metals occurs mainly through vegetable and animal products accumulating heavy metals from air, water and soil. Lead is deposited in the body by various tissues: blood (here it is 1-3%), soft tissues, hard tissues (here the most lead is about 95%). Lead in blood and soft tissues is a quick-change pool; in hard tissues - a slowly exchangeable pool, therefore the biological half-lives of lead are in: blood - 25 days; soft tissues - 40 days; hard tissues - 25 years.Chronic exposure to lead - mainly causes damage: 1.Haematopoietic system (inhibition of hemoglobin synthesis and shortening the survival time of red blood cells) 2.Nervous system - Lead crosses the blood-brain barrier - and lead encephalopathy (dementia, irritability, headache, muscle tremors, hallucinations, memory impairment and lack of concentration, convulsions, paralysis, coma), and (polyneuropathy - peripheral nerve damage syndrome) 3. Kidney - chronic nephropathy 4 High maternal lead concentration - linked to autism, fetal malformations, decreased IQ of children The mechanism of cadmium toxicity has not been fully understood, although it has been proven that its accumulation in cells causes oxidative stress. It is known that in the cell, cadmium binds to proteins rich in cysteine. It accumulates mainly in the liver and kidneys - which leads to a hepato and nephrotoxic effect. In case of mercury, the people are exposed to methylmercury. We observe clinical symptoms related to nervous system damage, changes in the peripheral nervous system - polyneuropathy, but also kidney lungs and musclesdamage. It has been shown that in women who have high levels of mercury in their body, neurological disorders can occur in the developing fetus. In food, apart from chemical pollutants, there are also biological contaminants (prions, viruses, bacteria, fungi, protozoa, helminths), which are the aetiological factors of infectious diseases. Table 1. Food infections Type of food infection Source Microorganism Intoxication Food containing bacterial toxins or mould fungal metabolites Clostridium botulinum Aspergillus flavus- mycotoxins Infection Food contaminated with pathogens that multiply mainly in the human digestive tract Escherichia coli – selected serotypes Campylobacter jejuni Salmonella and Shigella Toxicoinfection Food containing live cells that produce / release enterotoxins in the human digestive tract Escherichia coli – selected serotypes Clostridium perfringens Bacillus cereus The most common pathogens transmitted by food are: Viruses: Norovirus infections are characterized by nausea, explosive vomiting, watery diarrhoea and abdominal pain. Hepatitis A virus can cause long-lasting liver disease and spreads typically through raw or undercooked seafood or contaminated raw produce. Bacteria:  Salmonella, Campylobacter, and Enterohaemorrhagic Escherichia coli are among the most common foodborne pathogens that affect millions of people annually – sometimes with severe and fatal outcomes. Symptoms are fever, headache, nausea, vomiting, abdominal pain and diarrhoea. Examples of foods involved in outbreaks of salmonellosis are eggs, poultry and other products of animal origin. Foodborne cases with Campylobacter are mainly caused by raw milk, raw or undercooked poultry and drinking water. Enterohaemorrhagic Escherichia coli is associated with unpasteurized milk, undercooked meat and fresh fruits and vegetables.  Listeria infection leads to miscarriage in pregnant women or death of newborn babies. Although disease occurrence is relatively low, listeria’s severe and sometimes fatal health consequences, particularly among infants, children and the elderly, count them among the most serious foodborne infections. Listeria is found in unpasteurised dairy products and various ready-to-eat foods and can grow at refrigeration temperatures.  Vibrio cholerae infects people through contaminated water or food. Symptoms include abdominal pain, vomiting and profuse watery diarrhoea, which may lead to severe dehydration and possibly death. Rice, vegetables, millet gruel and various types of seafood have been implicated in cholera outbreaks. Antibiotic resistance of pathogens occurring in food is becoming an increasingly serious threat. Antimicrobials are essential to treat infections caused by bacteria, however their overuse and misuse causes the emergence and spread of resistant bacteria, rendering the treatment ineffective. Resistant bacteria enter the food chain through the animals (e.g. Salmonella through chickens). Human infection / invasion with pathogens in food occurs by: - eating food of unknown origin, - eating raw or undercooked food, - eating unwashed vegetables and fruits, - drinking unboiled water, - lack of hygiene when preparing meals - lack of personal hygiene. Measures to prevent the spread of infectious and invasive diseases transmitted by food include: - thorough washing of products subjected to processing and consumed raw, - use of appropriate thermal food processing, - ensuring proper sanitary and hygienic conditions for the population, - prevention of soil fertilization with human faeces and prevention of using of sewage sludge not subjected to sanitary control, - care for public health, including bans on the consumption of meat not subjected to official control, - public education in the field of epidemiology of diseases related to the consumption of contaminated food. Long-term storage of food also promotes multiplication of microorganisms decomposing nutrients and changing the characteristics of products (taste, appearance, smell, nutrient content, energy value, etc.). Metabolism of microorganisms causes food spoilage, which results in economic losses, but may also promote occurrence of food poisoning. Characteristics of selected toxins present in food: 1. Toxins contaminating food: Botulinum toxin (BTX) A mixture of several protein substances, secreted by the Clostridium botulinum, is a neurotoxin that disrupts neurotransmission in peripheral cholinergic synapses by inhibiting the release of acetylcholine, causing flaccid paralysis. Currently, the most common form of poisoning is observed in infants (between 3 and 20 weeks of age) fed with honey containing C. botulinum spores. Enterotoxin It is produced by the comma-shaped bacterium Vibrio cholerae. It occurs in water and food (undercooked vegetables, seafood, unpasteurized drinks) contaminated by the faeces of a person suffering from cholera or a carrier of this bacterium. It causes abundant, life-threatening diarrhoea (mortality rate in the case of untreated cholera is ~ 60%). 2. Toxins naturally occurring in food: Soybean inhibitor (SBI) Soybean inhibitor of trypsin, an enzyme responsible for protein digestion. It occurs in seeds of legumes soybeans, beans, broad beans, peas. It is a protein substance denaturing under the influence of temperature. It constitutes 6% of total proteins in soybeans and 2.5% in beans. Research results indicate that frequent consumption of trypsin inhibitors causes enlargement and chronic disease of the pancreas. Tetrodotoxin (TTX) Strong toxin present in the gonads and liver of fish of the genus Sphoeroides [Tetraodontiformes, e.g. fugu fish (bogeo / bok, hétún) used in Japanese cuisine], and also in certain species of starfish, crabs, octopuses, newts and salamanders. TTX is thermostable and has a very low lethal dose (DL 50=8μg/kg per os). It is formed with the participation of symbiotic bacteria from the genera Pseudomonas and Vibrio; the TTX generation and accumulation mechanisms have not been fully understood yet. Despite a very careful procedure of fish cleaning, it is estimated that about 100 people die each year as a result of fugu consumption, whereas mortality rates due to poisoning reach 60%. Symptoms caused by TTX poisoning can be divided into 4 stages (based on the amount of absorbed toxin): 1. Paraesthesia - the feeling of numbness, tingling or stinging. 2. Numbness of the face and tongue, mild psychomotor disorders. 3. Weakness of the muscles, breathing disorders, aphonia (inability to produce voiced sound). 4. Hypoxia, bradycardia, arrhythmia, coma, death. Parasites in food Some parasites (e.g. fish-borne flukes) occur naturally in food and are only transmitted with it, while others (e.g. tapeworms) can infect humans through food or direct contact with animals, and still others (e.g. Giardia intestinalis or Cryptosporidium) can contaminate fresh products through water or soil. Parasites whose invasive stages are naturally present in raw food:  in fish: Chinese liver fluke- Clonorchis sinensis (metacercariae), herring worm - Anisakis simplex (larvae), broad fish tapeworm - Diphyllobothrium latum (larvae);  in crabs: Oriental lung fluke - Paragonimus westermani (metacercariae);  in pork: trichina worm - Trichinella spiralis (encysted larvae), pork tapeworm - Taenia solium (larvae), Toxoplasma gondii (tissue cysts);  in beef: beef tapeworm - Taenia saginata (larvae), Toxoplasma gondii (tissue cysts);  in other meat of farmed animals (mutton / lamb, poultry) - Toxoplasma gondii (tissue cysts);  on the plants: sheep liver fluke - Fasciola hepatica (metacercariae). Parasites whose invasive stages may contaminate food:  food or water contaminated by human and/or animal faeces: Etamoeba histolytica (cysts), Giardia intestinalis (cysts), Cryptosporidium parvum (oocysts), Taenia solium (eggs), Ascaris lumbricoides (eggs);  food contaminated with canine and canid faeces: hydatid worm- Echinococcus granulosus (eggs), E. multiocularis (eggs), dog roundworm - Toxocara canis (eggs);  food contaminated with feline faeces: Toxoplasma gondii (oocysts), feline roundworm - Toxocara cati (eggs). References: 1. European Food Safety Authority, European Centre for Disease Prevention and Control. The European Union summary report on trends and sources of zoonoses, zoonotic agents and food-borne outbreaks in 2016. EFSA Journal 2017,15(12); 5077 2. Bane V. Tetrodotoxin: Chemistry, Toxicitity, Distribution and Detection. Toxins 2014, 6: 693-697 3. Buczek A.: Parasitology for medical students. Koliber Lublin, Second Edition. 2007 4. https://www.asbestos.com/asbestos/ 5. WHO