Chemical substances cancer-causing

Hazard Identification. Does a chemical substance or mixture cause adverse human health effects, such as cancer, birth defects, neurological damage, etc While It would be useful to have an unequivocal positive or negative answer to this question, that Is rarely possible. The usual situation Is that similarity to... 

Cancer. No studies have been conducted in human populations to determine whether mirex or chlordecone causes cancer. However, studies in mice and rats have demonstrated the ability of mirex to cause liver tumors (Innes et al. 1969 NTP 1990 Ulland et al. 1977a), pheochromocytomas (NTP 1990), and rare renal tumors (NTP 1990). A study in mice and rats also showed the ability of chlordecone to increase liver tumors (NC11976). As indicated above, available data on the genotoxicity of mirex and chlordecone indicate that these chemicals do not cause cancer by a mutagenic mechanism but rather by tumor promotion. Both mirex and chlordecone are considered by the DHHS to be substances that may reasonably be anticipated to be carcinogens and by IARC to be possible human carcinogens. EPA has not classified mirex or chlordecone as to their carcinogenicity. 

But we are moving too quickly. Before we can begin to contemplate the contribution of all these environmental carcinogens to the total cancer problem we need to acquire a better understanding of what is meant by the terms carcinogen or cancer-causing chemical and of how certain substances get to carry these labels. 

Following identihcation of the Rous sarcoma virus, a substantial number of additional tumor-causing (oncogenic) viruses have been identified. We are left with the key question of how to reconcile two observations on the one hand, chemicals or chemical substances cause cancer, on the other hand, viruses cause cancer. These observations split the oncology community into two camps. As frequently happens in science, neither camp had the full story and the two opposing viewpoints proved to be entirely compatible. 

OECD has also published a document on a Harmonised integrated classification system for human health and environmental hazards of chemical substances and mixtures (OECD 2001b). Chapter 2.6 addresses a harmonized system for the classification of chemicals, which cause cancer. 

Carcinogen a substance that causes cancer Catabolism metabolic processes where molecules are broken down Catalysis chemical process in which a reaction rate is accelerated Catalyst a substance used to accelerate a chemical reaction without taking part in the reaction... 

Stochastic Responses. A basic principle of health protection for both radionuclides and hazardous chemicals is that the probability of a stochastic response, primarily cancers, should be limited to acceptable levels. For any substance that causes stochastic responses, a linear dose-response relationship, without threshold, generally is assumed for purposes of health protection. However, the probability coefficients for radionuclides and chemicals that induce stochastic responses that are generally assumed for purposes of health protection differ in two potentially important ways. 

However, given the current state of knowledge and methods of dose-response assessment for substances that cause stochastic responses, there appear to be important technical and institutional impediments to the use of either incidence or fatalities exclusively. Data on radiation-induced cancer incidence and chemical-induced cancer fatalities for use at the low doses and dose rates relevant to health protection are not readily available, and current regulatory guidance calls for calculation of cancer incidence for hazardous chemicals. Since use of a common measure of response for all substances that cause stochastic responses may not be practical in the near term, both measures (fatalities for radionuclides and incidence for hazardous chemicals) could be used in the interest of expediency. The primary advantage of this approach is that the measures of stochastic response for radionuclides and hazardous chemicals would be based on the best available information from studies in humans and animals, and it would involve the fewest subjective modifying factors. This approach also would be the easiest to implement. 

DNA molecules may be modified by the unintentional addition or deletion of nucleotides or by substituting one nucleotide for another. The result is a mutation that is transmittable to offspring. Mutations can be induced by chemical substances. This is a major concern from a toxicological viewpoint because of the detrimental effects of many mutations and because substances that cause mutations often cause cancer as well. DNA malfunction may result in birth defects, and the failure to control cell reproduction results in cancer. Radiation from x-rays and radioactivity also disrupts DNA and may cause mutation. 

Carcinogen Any substance or chemical that can cause cancer in animals or humans. 

Society would not look the same without man-made chemicals, being of utmost importance in medicine, industry and agriculture and for the daily welfare of citizens (European Commission 2009). At the same time, the production and use of many chemicals are causing severe health and environmental problems, including allergies, cancer and decline of biodiversity (see e.g. EEA 2007 EEA1998) in fact, 70% of new chemical substances assessed under EU law have at least one property that is dangerous to the environment (European Commission 2003). Adverse effects result from the continued use of well-known hazardous substances and from new chemicals that are introduced without much control, not least chemicals found in... 

Cancer-Causing Chemical Substances and Occupation Affected... 

Latency period The period of time between exposure to something that causes a disease and the onset of the health effect. Cancer caused by exposure to chemical substances may have a latency period of 5-40 years LDH Lactate dehydrogenase... 

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