The harmful substances produced by microbes, which can cause damage to living organisms, are called toxins. These toxins can be produced by various types of microorganisms such as bacteria, fungi, and viruses. Toxins can have detrimental effects on the host organism by disrupting cellular processes, damaging tissues, and causing disease symptoms. It is important to note that toxins are different from antibiotics, hormones, and pollutants. Antibiotics are substances that can kill or inhibit the growth of bacteria, hormones are chemical messengers produced by the body to regulate various bodily functions, and pollutants are substances that contaminate the environment and can have harmful effects on living organisms. Therefore, the correct answer is option 4, toxins.