In the last two decades implausible expansion in industrialization and urbanization has been noticed globally. This expansion
and lack of environmental regulation has lead to a large input of various toxic pollutants into the
atmosphere. Since these hazardous chemicals have become a part of our food-chain, human exposure to these chemicals is inevitable and has produced escalating risks. Of immediate concern is the release of various heavy metals like Pb, Hg, Cd, Ni, Zn etc. due to different anthropogenic activities. Thus continuous
monitoring of air quality is pre-requisite. This can be accomplished either by the construction of computer models, mechanical collectors or by the employment of bio-indicators/ biomonitors. Bioindicators generally refers to all organisms that depict the quality of the environment on the basis of changes in morphology, physiology etc., however biomonitors provide both qualitative and quantitative information. This use of organisms as monitors of the environment is known as “biomonitoring” and the organisms are known as biomonitors. On the basis of origin, biomonitors can be further classified into passive biomonitors (employs organisms that occur naturally in the study area) that were first used at the end of 1960s and active biomonitors (organisms are transplanted in the research area for few days to months). Passive monitoring is perfect for long-time monitoring processes and is most frequently used. The advantage of active monitoring is however, that it is performed in those study areas where naturally growing monitors are absent e.g. in heavily polluted areas. The most preferred organisms are those that are able to accumulate the pollutants, be available throughout the year, easy to capture and identify, be relative sedentary and are cosmopolitan in distribution. Further the accumulated pollutants should be easily measured and measurements should provide the information about the level of pollutant deposition. Mosses and lichens as well, are considered as the most appropriate plant material to study the atmospheric deposition of heavy metals, yet pine needles, tree bark, mushrooms have also been used to monitor persistent toxic pollutants including heavy metals. Mosses are small, cryptogamic plants that thrive well in damp areas marked with high humidity and frequent rainfall. They have simple thalloid or one-cell thick structure, lacking true stems, leaves or roots. They also lack cuticle or epidermis thus are directly dependent on the atmosphere for the supply of nutrients. Inevitably they also accumulate pollutants both from precipitation and dry deposition. Mosses also have high cation-ion exchange (CEC) property, have slow growth rate, undeveloped vascular bundles and are world-wide in distribution. These properties make them the most ideal organisms for biomonitoring of heavy metals in the atmosphere. Besides ease of sampling, identification of sources and emissions, economical aspects also have to be considered. It is here that mosses could be used for biomonitoring of air-borne heavy metals. Biological monitoring has several advantages over several other ways that are employed to study an integrated picture of airborne pollutants. The use of moss species as environmental monitors is much cheaper than the use of mechanical collectors. Monitoring by mosses is possible simultaneously in tens of thousands of observation points. Further chemical analysis is strongly dependent on the time and place of sampling. If the pollutants released are readily dispersed, their concentration in the atmosphere will fall below the detection limit and thus escape notice, whereas bryophytes have the ability to facilitate the detection of the elements present in very low concentrations. Moreover mosses can be stored for several years without noticeable deterioration and old specimens can easily be chemically analyzed. Thus a comparison between fresh and herbarium specimens can be performed. It is still noticeable that both herbarium and fresh specimens should originate from the same locality and provides a good insight of the past and present heavy metal burden at the research area. Thus bryophytes can serve as “Environmental Specimen Banks”. One such environment specimen bank has been established by Kubin and co-workers at Finland.