Assessment of Exposure to Chemical Contaminants PDF

Machine Translated by Google Assessment of exposure to chemical contaminants Chemical and biological environmental hazards Machine Translated by Google Chemical and biological environmental hazards 9...

Machine Translated by Google Assessment of exposure to chemical contaminants Chemical and biological environmental hazards Machine Translated by Google Chemical and biological environmental hazards 9 Assessment of exposure to chemical contaminants 1. Exposure to chemical contaminants. RD 374/2001. Valuation criteria To evaluate exposure to chemical contaminants, it is important to follow the procedures, criteria and recommendations provided by RD 374/2001 and the technical guide that it develops. Assessing will ultimately consist of comparing the environmental situation studied with previously defined values or assessment criteria and determining the need to intervene to avoid harm to health. 1.1 Exposures to chemical agents. RD 374/2001 Royal Decree 374/2001, on the protection of health and safety of workers against risks related to chemical agents during work, explains what the procedure for action should be when exposure to chemical agents occurs. The Technical Guide for the evaluation and prevention of the risks present in the regulations relating to chemical agents provides criteria and recommendations that can facilitate the interpretation and application of RD 374/2001. L'RD 374-2001 must be applied whenever contaminants are present in the work environment. 1.1.1 Previous definitions L'RD 374/2001 understands with exposure to chemical agents the presence of a chemical agent at the level of work that implies the contact of this agent with the workers, normally by inhalation or by dermal route. Because the exposure of a worker to a chemical agent is produced, two requirements must therefore be met: Presence of chemical agents 1. What followed was presented to the lloc de treball. A chemical agent can be presented to the lloc The evaluation of rocks has to foresee all the chemical agents present of treball for different reasons: in the work process, regardless of who followed their origin. Use the first material. It is manufactured or generated as an intermediate product, waste or impurity not volguda. Machine Translated by Google Chemical and biological environmental hazards 10 Assessment of exposure to chemical contaminants It is a form or intervention in complementary operations of maintenance, repair, emmagatzematge, cleaning, disinfection of works, modifications, etc. S'emmagatzema temporarily or permanently. Penetrates from the outside. These are general employment benefits for non-work activities. 2. I made contact with both workers. When there is no possibility of contact between the workers and the chemical agent, not parlem d'exposició. Unagent químic perillos (AQP) is a chemical agent that can represent a risk for the safety and health of workers for the various physical, chemical and toxicological properties or for the way in which it is present or used in the work code. Dins of this group of perillosous chemical agents, the RD includes: The chemical agents that complicate the criteria for being classified as perillosos in the regulations for the marketing of substances and preparations, regardless of whether they are classified or not in these regulations. The chemical agents that have an environmental limit value in the RD itself (with lead and its derivatives) or in a legal provision or in the professional exposure limits document (LEP) of the INSHT. You can expand the information on environmental limit values in the section “Valuation criteria or limit values” of this nucleus of activity. 1.1.2 Procedure for action The regulations establish what the procedure for action should be in cases of exposure to chemical agents (figure 1.1). This procedure can be summarized in the following phases: 1. First of all, the company must determine if there are chemical agents perillosos to the lloc de treball. 2. How dangerous chemical agents are trying to evaluate the risks that origin quan: (a) the results of the assessment determine that there is a risk, it is necessary to apply specific measures of prevention and protection, health surveillance and measures in the case of accidents, incidents and emergencies; Yo (b) the results of the evaluation determine that if there is only one risk, the application of the general principles of preventive action will be sufficient. Machine Translated by Google Chemical and biological environmental hazards 11 Assessment of exposure to chemical contaminants Figure 1. 1. Procedure of action in case of exposure to chemical agents 1.1.3 Risk assessment The risks that can be evaluated derived from the presence of chemical agents are the following: risk of fire and/or explosion, of perillose chemical reactions, by inhalation, by absorption through the pell, by contact with the pell or the ulls , by ingestion and by penetration parenterally. Example of information for cliff assessment Information for cliff assessment An example of information necessary for the duration of risk assessment is the ability of chemical agents to penetrate the When evaluating the cliffs originating from the AQP, RD 374/2001 establishes that they must be organism via the dermal route. taken into account: In the core of activity “Fonts of information on chemical 1) The property owners of the AQP and any other information necessary to evaluate the cliffs. contaminants” of the didactic unit The regulations on product marketing establish that the supplier is obliged to provide this “Industrial hygiene. “Chemical contaminants” can provide information. Specifically, you must provide the product label, the safety data set and the more information on labels and safety precautions. recommendations made by the European Commission on the results of the evaluation. of the risk and on the limitation of the risk. 2) The limit values. They must take into account, first of all, the environmental and biological limit values that have been established in RD 374/2001 itself or in an other legal provision; In the absence of these values, they are established in the INSHT Professional Exposure Limits document and, ultimately, they are established in similar internationally recognized documents (for example by ACGIH). Machine Translated by Google Chemical and biological environmental hazards 12 Assessment of exposure to chemical contaminants 3) The quantitats of the chemical agents presented in the labor code. 4) The type, intensity and duration of the exposure is another factor that affects the magnitude of the risks derived and also the accidental exposures. Quantity of chemical agents The volumes used for a given Example of factors that affect the magnitude of the cliffs product in a small research laboratory will surely be much lower than those used in an industry in which it It is not essential to work with a chemical agent using a laboratory display case, which is intervenes as raw material in the on a table. production process. This factor is essential to keep in mind It is not safe to use ammonia diluted with the neteja product, in low concentrations, when carrying out the final evaluation than to use it in a production process at high concentrations. of cliffs. It is not advisable to sporadically use a chemical agent that works all day long. labor. Etc. All of these factors, therefore, must also be considered when evaluating the risk. 5) Qualify for other fire conditions that influence the risks related to the presence of chemical agents in the fire hazard and, in particular, fire hazards and explosions. Example of work conditions that affect the risk of ingesting the 6) Effect of preventive measures adopted or intended to be adopted. The technical guide most significant factors or conditions that says that the risk must be evaluated as it is at that moment, that is, the prevention need to be taken into account to evaluate-these are personal measures that are currently in use must be taken into account. Likewise, the measures hygiene habits, the possibility of eating, drinking or smoking that are expected to be adopted in exceptional situations such as emergencies, etc. must at work. , the presence of especially sensitive workers, also be considered. Simultaneous exposure to various chemical agents and the use of inappropriate work procedures. 7) Conclusions from the health surveillance of workers. The conclusions on health surveillance can warn about workers' exposure to different contaminants and provide a better assessment of the risks present. 8) Accidents or incidents caused or potentiated by the presence of chemical agents at work. Company accident data are an important source of information when assessing chemical risk. Measures The evaluation of the risks derived from inhalation exposure to an AQP has included the measurement of the concentrations of the agent in the air and the comparison of this value with the corresponding environmental limit value. This measure must be representative of the exhibition. Therefore, they must pay special attention to the respiratory zone of the workers and in the conditions regular workers. When it is clearly demonstrated, by other measures, that prevention and patient protection has been achieved, these measures will not be necessary. To save personal items, portable display bombs are useful. Machine Translated by Google Chemical and biological environmental hazards 13 Assessment of exposure to chemical contaminants Therefore, they do not take into account the duration of the term measures: When the technical personnel consider, take into account the working conditions, which practically have not been exposed or that the concentrations to the environment are too low to meet the limit values. When the technical staff considers that it is essential to implement measures specific prevention measures. If, in accordance with the above criteria, it is decided not to take a long time, it is necessary to document and explain the reasons why this decision was made. In some cases it is not possible to measure Cliff assessment update It is not necessary to measure whether effects attributable to the exposure have occurred and it is necessary to apply specific prevention The working conditions are not static, but rather changeable. To guarantee the safety and health of measures to correct the situation. workers and maintain the effectiveness of the prevention and protection measures implemented, risk assessment must be updated. According to the technical guide, the updating of the evaluation consists of a review of the evaluation of the cliffs that allows detecting or reassessing causes and factors that are missing or that have varied over time, with the objective of verifying the suitability of the measurements preventives implemented, or, if necessary, implement new measures or modify-ne les existents. The regulations establish that the evaluation of cliffs must be reviewed: How do you modify the working conditions, so that you can increase take the risk. There was a specific regulation that required review. How are the effects detected on workers' health? When it is detected that prevention measures are inadequate or insufficient. Periodically, according to who follows the effects on health and the characteristics of the work processes. Health surveillance will make it possible to detect effects of pollutants on health and review the evaluation of cliffs as they are escaigui. 1.1.4 Risk of loss It is possible to define a risk with the remote probability that it is a risk, which in all cases, would be of small magnitude. Machine Translated by Google Chemical and biological environmental hazards 14 Assessment of exposure to chemical contaminants The nomenclature of “risc lleu” used by the RD is an imprecise term. In many cases it is difficult to make a decision on whether or not the risk is valid. A risk can be more or less light, but it is complicated to establish the limit that separates the light risk from the one that is not. In the case of the risk of exposure to chemical agents, the technical guide establishes some criteria regarding the risk of exposure to inhalation of a chemical agent: For sensitizing agents, carcinogens, mutagens or toxicants for reproduction there are no risk. That is to say, there are no safe exposures and they have always applied specific measures of prevention and protection, health surveillance and measures in the case of accidents, incidents and emergencies. However, it is not considered a risk because it is associated with sensitivities, carcinogens, mutagens and toxicants for reproduction. For chemical agents with environmental limit values defined to avoid irritations, injuries, etc., which are easily perceptible to workers, do not take specific measures if these effects are not produced. For the rest of the chemical agents: – If the exposure is less than or equal to 10% of the environmental limit value, do not cal apply-hi specific preventive measures. – If the exposure is greater than 10% of the environmental limit value, specific prevention and protection measures, health surveillance, etc. must be applied. It is not considered a risk when environmental limit values are exceeded. established in the RD or in the LEP document of the INSHT. 1.1.5 General principles of preventive action L'RD 374/2001 establishes that the risks for the health and safety of workers must be eliminated or reduced to a minimum through the application of the general principles of preventive action. Machine Translated by Google Chemical and biological environmental hazards 15 Assessment of exposure to chemical contaminants The general principles of preventive action: The conception and organization of the work systems at the work level. The selection and installation of work equipment. The establishment of adequate procedures. The adoption of hygienic measures for patients, both personal and personal and clean. The reduction of the AQP quantitats presented to the labor tax min. Reduced to a minimum the name of workers exposats and the duration and intensity of the exhibitions. In the teaching unit “Chemical Risk Prevention and Protection” you can expand the information on the general principles of preventive action. 1.1.6 Specific prevention and protection measures When the elimination of the risk was not possible, it would take time to reduce the application of prevention and protection measures to a minimum. These measurements are included in the order of priority: 1. The conception and use of work procedures, technical controls, equipment and materials to avoid or reduce any leakage, diffusion or direct contact with workers. 2. Ventilation measures or other collective protection measures. 3. Individual protection measures. In the teaching unit “Chemical Risk Prevention and Protection” you can expand the information on the specific prevention and protection measures. 1.1.7 Health surveillance When the risk assessment manifests a risk to the health of workers, employers must constantly monitor the health of workers. The employer must inform workers about exposing them to a chemical agent for which health monitoring remains mandatory. If health surveillance effects are detected due to exposure to an AQP or the biological limit values are exceeded, it will take time to review the risk assessment and the measures planned to eliminate or reduce the risks, take into account recommendations of the responsible metge, maintain surveillance of the health of the Affected workers and examine all exposed workers. Machine Translated by Google Chemical and biological environmental hazards 16 Assessment of exposure to chemical contaminants 1.1.8 Measures to be taken in case of accidents, incidents and emergencies The company must plan the activities that it carries out in cases where accidents, incidents or emergencies occur and must adopt the necessary measures so that it can correctly carry out the planned activities. The measures to be adopted, according to RD 374/2001, include: The provision of equipment is necessary to reduce the consequences and to control the situation of perill and for the evacuation of workers and first aid (when calgui). It is necessary to plan actions in the event of an emergency. The theoretical and practical training of the workers who participate in the activities. tattoos are mentioned. The organization of relations between those serving outside the company: firefighters, medical assistance, etc. Accessibility of information on emergency measures related to AQP. Establishment of the necessary communication and communication systems. 1.2 Valuation criteria or limit values The evaluation of risks is based on comparing the concentration levels of the chemical agents in the air, with the evaluation criteria or previously defined limit values. These values are established so that individual concentration levels of a given chemical agent do not generate effects on the health of workers. The lower the limit value of a substance, the more perillorous it is. The limit values are the values that are used, in the evaluation of the chemical risk, to compare both the results obtained from the work environment. The assessment criteria establish exposure to a chemical agent that is considered acceptable. 1.2.1 Obtaining limit values The limit values are obtained from epidemiological studies, animal or human experimental studies, by analogies between chemical agents and industrial experience. Machine Translated by Google Chemical and biological environmental hazards 17 Assessment of exposure to chemical contaminants To establish the limit value of a chemical agent, it is necessary to take into account its toxicity, its absorption capacity via inhalation and its ability to accumulate in the body. Conditions of limit values The study of dose-effect and dose-response relationships makes it possible to quantify the toxic All limit values have a scientific effects of chemical agents and is the theoretical basis for establishing valuation criteria. basis, but they may be conditioned by technical, economic and social factors. To define the limit values, it is necessary to follow the following steps: 1. Study the dose-effect relationship, that is, the relationship between the magnitude of The exposure to the substance (dosage) and the intensity of the effect. 2. Study the dose-response relationship, that is, the relationship between the magnitude of the exposure to a substance (dose) and the name of the individuals they present a determinant effect. 3. Decide who is the maximum effect that can be tolerated. 4. Decide who is the percentage of the population that must be protected. 5. Deduce the corresponding maximum dose according to the percentage of the population that It must be protected and the maximum effect that can be tolerated. 6. Establish the exposure limit value so as not to exceed this dose. 1.2.2 Regulations Some specific regulations define the limit values of certain substances: L'RD 374/2001, on chemical agents, including the limit values for lead inorganic and its derivatives. L'RD 1124/2000, on carcinogens, includes the limit value for gasoline the air. L'RD 349/2003, modification of L'RD 1124/2000, established the limit value per to vinyl chloride monomer. Directive 98/24 establishes that member states of the European Union must define national valuation criteria or exposure limit values. L'RD 374/2001 determines that the limit values that are used as reference values for the evaluation and control of the risks originating from the exposure of workers to chemical agents, are the professional exposure limits (LEP) emesos per l'INSHT. Machine Translated by Google Chemical and biological environmental hazards 18 Assessment of exposure to chemical contaminants The professional exposure limits (LEP) are defined with the reference values for the evaluation and control of the risks inherent to the exposure, mainly for inhalation, the chemical agents present at the occupational level and, therefore, to protect the health of the workers and their offspring. The INSHT annually publishes the document Professional exposure limits for chemical agents in Spain (LEP document) which contains these professional exposure limits. In the LEP document, which is published in both electronic and paper format, two types of limit values are established: the environmental limit values (ELV), the biological limit values (VLB). 1.3 Environmental limit values (ELV) and environmental control During the evaluation of exposure to a chemical contaminant, the highest concentration is generally measured at the level of work. Això is the one that is coneix com to environmental control. An environmental limit value is a reference value expressed as the limit concentration of contaminants at the level of work for a period of determined times. The environmental limit values of concentration in Spain are associated with an exposure The comparison between the value measured in environmental control and the reference value time of 15 minutes or 8 hours. (environmental limit value) allows us to determine whether or not there is a risk for the health of workers. 1.3.1 Environmental limit values for Spain The LEP document defines the environmental limit values (ELV) as reference values for the concentrations of chemical agents in the air and represent conditions under which it is believed, according to current knowledge, that the majority of workers may be exposed. Day after day, during your working life, there are no adverse effects on your health. We can therefore test both substances which are currently not associated with adverse effects, but which have also been shown to have detrimental effects on the health and safety of workers. For this reason and because knowledge about substances and their effects is continually advancing, environmental limit values are to be reviewed every year. Machine Translated by Google Chemical and biological environmental hazards 19 Assessment of exposure to chemical contaminants It should be noted that the definition says that the limit values protect the majority of workers, not all. Despite the individual differences between people, there may always be a small percentage of workers who experience exposures below the limit values. The VLA does not guarantee absolute The environmental limit values are reference values that are only used to evaluate the risks protection. The limit of inhalation. values cannot be considered limits between illness and health, that is to say, not exceeding them When a chemical agent is also absorbed through the dermal route, it should be included in does not imply that it does not produce a negative effect or exceeding them, the list with the notation “dermal route”. In this case, it must be taken into account that the which is contrary to professional illness. measurement of environmental exposure may not be sufficient and measures must be taken to avoid this skin absorption. Units of environmental limit values The environmental limit values are defined in the LEP document in the units following: For gases and vapors they are given in ml/m3 (ppm), a unit independent of pressure and temperature, or in mg/m3 at 20 ºC and 101.3 kPa. Per non-fibrous particulate matter in mg/m3. Per a fibers in fibers/m3 or fibers/cm3. Definitions The LEP document establishes a series of definitions: The breathing zone is the open space of the workers' faces. which catches the air they breathe. Daily exposure (ED) is the average concentration of the chemical agent in the workers' breathing zone measured or calculated in a time-weighted manner, for the actual working day and referring to a standard workday of 8 hours a day.. Short-term exposure (CS) is the average concentration of the chemical agent in the workers' breathing zone measured or calculated for any period of 15 minutes throughout the workday. In the core of the activity “Calculations to assess exposure to chemical Types of environmental limit values agents” you can see how the ED and EC values are calculated. The LEP document establishes two types of environmental values: the environmental limit value-daily exposure (VLA-ED) and the environmental limit value- duration exposure limit (VLA-EC). Machine Translated by Google Chemical and biological environmental hazards 20 Assessment of exposure to chemical contaminants The VLA-ED is defined as the reference value for daily exposure (ED). They represent conditions under which it is believed, according to current knowledge, that the majority of workers can be on duty for 8 hours a day and 40 weeks, during their working life, without having adverse effects on their health. The daily exhibition (ED) cannot exceed the VLA-ED. The VLA-ED protects workers from chronic effects, that is, from the effects that can cause long-term professional illnesses. The VLA-EC is the reference value for short-term exposure (EC). The VLA-EC protects workers from harmful effects. The VLA-EC cannot be exceeded per short exposure cap (EC) throughout the working day. The substances can have defined the VLA-ED, the VLA-EC or the two limit values. When a chemical agent defines a VLA-ED and a VLA-EC, the exposure must be evaluated with respect to the two values and to be considered acceptable, they must be respected simultaneously. VLA-ED and VLA-EC When the VLA-EC has not been defined in a substance, it is not possible to exceed the product 3 Chemical agents that have acute effects and chronic natural effects have a defined VLA-ED and a VLA-ED for more than half an hour in a work day and it is not possible to exceed more than 5 VLA- VLA-EC and, therefore, both limit values ED. must be taken into account in the evaluation. 1.3.2 International environmental limit values The main institutions that have published environmental limit values to the State Units are: the Occupational Safety and Health Administration (OSHA), the National Institute for Occupational Safety and Health (NIOSH) and the American Conference of Governmental Industrial Hygienists (ACGIH). OSHA publishes PEL (permissive exposure limits) values, which are the regulatory values of the Statistical Units. NIOSH publishes REL (recommended exposure limits) values or recommended exposure limits. The REL values include two types of limits: REL-TWA: average exposure values for periods from the end to 10 hours. REL-C: maximum exposure values for periods of 15 minutes or less. ACGIH publishes and annually reviews TLV values (threshold limit values) or limit values. Machine Translated by Google Chemical and biological environmental hazards 21 Assessment of exposure to chemical contaminants The values published by the ACGIH are the ones with the most prestige on an international scale and are the basis for most Western countries when defining their own limit values. ACGIH The TLVs that define the ACGIH are: ACGIH is a private institution in the USA, founded in 1939, which brings together professionals in the field of industrial hygiene. 1. TLV-TWA (threshold limit value - time weighted average). Limit value The TLV-TWA value is similar to that llindar-mitjana weighted in the temps. defined by the INSHT as the VLA-ED. It corresponds to the average concentration weighted in time, for a normal working day of 8 Spanish regulations do not define a hours/day and 40 hours/week, to which the majority of workers cannot be exposed repeatedly value equivalent to the TLV-C value. day after day without leaving. The TLV-STEL value is similar to the adverse effects. INSHT definition of VLA-EC. The TLV-TWA allow deviations as long as it is compensation for both deviations per sota and as long as they do not exceed the TLV-STEL values. 2. TLV-C (threshold limit value - ceiling). Sustained limit value. It corresponds to the concentration that cannot be exceeded in the instant. Normally this value is defined by substances that have a very intense action and both immediate effects on health. 3. TLV-STEL (threshold limit value - short term exposure limit). Limit value Short-term exposure limit. It corresponds to the concentration to which the workers can be exposed during a continuous period of temperatures from late to 15 minutes without causing irreversible or intolerable damage. It is not a separate and independent exposure limit but rather a complement to the time- weighted index (TWA). The TLV-STEL must not be exceeded at any time during the day. Exposures to the TLV- STEL must not be longer than 15 minutes and must not be repeated more than four cops per day. As a minimum, you should allow one hour to pass between the two presentations at the TLV-STEL concentration. Few substances have the TLV-STEL definition. If there is no TLV-STEL in a substance, it is not possible to exceed the product 3 TLV-TWA for more than half an hour in a work day, and it is not possible to exceed 5 TLV-TWA. The TLV-TWA and TLV-STEL values published by the ACGIH and the VLA-ED and VLA- EC values published by the INSHT are similar, but there are differences in some of these values. MAC value In the USSR, MAC values (maximum permissible concentrations) are defined. The MAC value corresponds to the maximum permissible concentration of a harmful substance in the air of the work area that, if not exceeded during an 8-hour work day (or an additional period of 41 hours/week) over a period of The entire active life of an individual is able to guarantee that he or she will not manifest maldiatry or deviation from normal status. of detectable health using usual methods, both during working life and afterwards, both in the present generation and in them properes. Machine Translated by Google Chemical and biological environmental hazards 22 Assessment of exposure to chemical contaminants They are very safe values from a preventive point of view, but technically difficult to comply with today. 1.4 Biological limit values and biological control The environmental limit values are used as a reference when there is an environmental control: that is, when measuring the concentration at the level of work. However, this does not mean either environmental control but rather biological control (measured by the workers themselves). In these cases, we must go through the biological limit values to make the comparison between the values. measured. 1.4.1 Biological control Biological control must complement, in many ways, environmental control. Biological control is the evaluation of the total exposure to a chemical agent based on the levels of a biological indicator observed in a biological medium of the workers with a sample placed at a specific time of the day, by comparison with some values of reference. It is a matter of evaluating the total exposure, because what is measured is the dose actually received by the worker, regardless of his origin and the route of entry into the organism. From the definition of biological control we can deduce who are the four basic elements involved in biological control: the biological indicator, the biological medium, the moment of display and the reference values or biological limit values. These elements must always be defined in biological control. Biological indicator (BI) Examples of biological indicators Exposure to cobalt is measured from The biological indicators are the parameters that are measured in a biological medium of the the concentration of cobalt in blood or urine. That is, cobalt is the workers and are associated with the chemical agent to which the workers are exposed. chemical agent that must be measured and the biological indicator. Furthermore, exposure to ethylbenz can be measured from the concentration of mandelic acid in urine. That is, mandelic In some cases, what is measured is the concentration of the chemical agent itself. It is the case of acid is a biological indicator of ethylbenz. molts metalls. In other cases, it is necessary to measure other substances. This is the case of molts solvents. When a biological limit value is defined for a chemical agent, it indicates which biological indicator must be measured. Machine Translated by Google Chemical and biological environmental hazards 23 Assessment of exposure to chemical contaminants Biological medium or specimen With biological medicines there are basically three uses: 1. Urine. The advantages of using urine as a biological medicine are that it is available from accessible samples, which can be extracted in large volumes and the analysis methods are simple. The concentration of a contaminant in urine It may present great variability depending on the volume of liquid excreted. For this The collection and analysis of urine samples are simple. reason, the results are correct and are always expressed in reference to some substance that had a behavior, when excreted, similar to that of the contaminant (in many cases creatinine). The biological limit value for the arsenic level in urine is 5 g/g creatinine. 2. Sang. When it is caused by exposure to a chemical agent, the concentration in blood presents few variations between the different workers exposed; That is to say, it is a reliable data that conveys an idea of this exposition. The disadvantages of using blood as a biological medium are that it is subject to an invasive sample, that the analysis methods are more complex and that the samples deteriorate easily. 3. Exhale air. Exhaled air can only be used as biological media as it contains volatile Blood analysis provides reliable data. substances. In this case it is also the tract of a non-invasive sample. Moment of the monster The recommended moments for the display must be scrupulously respected, as they are defined based on the average life of the indicator. The moments of showing people can be: For indicators that do not accumulate to the organism: they have just begun the I turned to finish it. For indicators that accumulate in the body: at the beginning of the week i at the end of the work week. For indicators that accumulate in the body during periods of very long periods (greater than 48 hours): it is not critical, it is possible to show it in any case. Interpretation of VLB moment. In the case of toluè, the VLB is 0.05 mg/ l blood and the VLA-ED is 192 mg/m3. For a worker who is exposed to an exposure exclusively by inhalation of the amount of 192 Reference values or biological limit values mg/m3 of toluè, the blood concentration will probably be approximately 0.05 mg/l. If in a person we determine a toluè concentration of, for example, 0.02 mg/l The biological limit value (VLB) corresponds to the level of the biological indicator blood, it is most likely that at the end of the day the toluè concentration remained of a chemical agent that can be observed in a biological medium by workers without lower than 192 mg/m3 (it is not possible to estimate the value, but risk for health. assume that the VLA-ED is not passed). Machine Translated by Google Chemical and biological environmental hazards 24 Assessment of exposure to chemical contaminants The biological limit values have been established by workers without being applicable to professional exposures of 8 hours/day, 5 days/week. The biological limit values are indicative. In general, VLBs represent the most likely levels of biological indicators in workers without exposure to a global exposure to chemical agents equivalent in terms of adsorbed dose to an exposure exclusively by inhalation of the VLA-ED. In Spain, the VLB is used annually in the LEP document of the INSHT. In this document it is recorded, for the chemical agents that have been defined, the biological indicators, the moment of display and the VLB and it is indicated in whom it was measured must be measured. The ACGIH also defines its biological limit values, the BEI or biological exposure indices. 1.4.2 Advantages and disadvantages of biological control The most significant contributions of biological control are the following: Tea in all the ways of penetration of the chemical agent and not only the inhalation route. Això is especially important in chemical agents that easily penetrate through the dermal route. Integrates work and non-work exposure. It could be that workers, in their private lives, in their habits, are exposed to polluting material. Take into account individual differences in responding to contaminants. Allows us to evaluate, in certain cases, old exhibitions, how the time of life from the indicator I allowed. Biological control allows us to really determine what Quant als seus inconvenientes, est can bement the economic cost raised and the many factors dose is collected by a specific individual. of variabilitat: the physiological state of the individual, the habits, etc. Finally, it should be noted that in the biological control the obtaining of the sample can be difficult and uncomfortable for the workers. 1.4.3 Applications Biological control is complementary to environmental control and should be used only when strictly necessary. Biological control is recommended in the following cases: To check environmental control. Machine Translated by Google Chemical and biological environmental hazards 25 Assessment of exposure to chemical contaminants To check the effectiveness of PPE. To determine absorption through a route other than the respiratory route. To detect non-occupational exposures. There are specific regulations that establish biological control. L'RD 374/2001 establishes that in the case of exposure to Biological control cannot be used alone to evaluate an exposure. lead, biological control must be carried out.