Why using bees to monitor environmental pollution?
Bee is a reliable indicator of environmental quality because she is daily in contact with several pollutants, on a large surface of exposure.
Natural samples on water/air/ground matrixes:
While foraging, bees naturally sample pollutants on the ground through nectar, pollen and honeydew collected on flowers and trees.
They also sample water when they drink in puddles and pits (a whole colony drinks around 100 liters of water per year).
Finally, an electrostatic field generated around their bodies catch all particles in suspension while they fly.
So, bee is an excellent and natural homogeneous bio-collector of pollutants.
A large radius of action:
We estimate that bees forage on a 1,5 to 3 km radius around their hive, depending on food quantity.
Claudio Porrini said : « If we take into account the fact that a hive contains around 40 000 bees, and that a quarter of them are foragers daily visiting a thousand flowers each, we can estimate that a colony daily does 10 millions of micro-samples. »
Bee is then an excellent pollutant sampler, on a surface going up to 27km².
How do we analyze pollutants collected by bees (APIDIAG© Method)?
From hives previously set up on an area to study, APIDIAG method consists in sampling bees to analyze them and quantify specific pollutants researched.
This method enables to realize comparisons:
- Spatially (realization of multiple samples on different sites at the same moment)
- Temporally (realization of successive samples in a year)
How to interpret results obtained?
Presentation of the Bee Index
Up to now, no regulatory thresholds concerning pollutant concentrations in bees were developed. Tools for results interpretation are depending on the family of analyzed pollutants.
For Heavy Metals and PAHs:
For Heavy Metals and PAHs, indexes for environmental quality were developed on the basis of national and international scientific publications and previous national sampling campaigns.
Values for the index were then split into 10 levels of pollution, in order to obtain a grade from 1 to 10. Finally, a description (from « Very Good » to « Bad ») was given for each category.
For other pollutants, such as PCBs, dioxins/furans, COVs and particles, there are no sufficient data to create a bee index for environmental pollution. Interpretation is then done by spatiotemporal comparisons.
From one part, concentrations are compared to values observed on a control apiary considered as representative of local background concentrations. From another part, variations in time are analyzed: seasonal and annual variations.
What are the pollutants detectable in the environment thanks to bees ?
We usually call heavy metals all natural metallic elements which volumetric mass is higher than 5g/cm3. We can often find them under small quantities in the environment. Toxicological impact of heavy metals depends on their chemical form (named "chemical species"), their concentration, the environmental context, their biodisponibility and their availability to pass through the trophic network. The most toxic are Lead, Cadmium and Mercury.
Most researched elements: Antimony (Sb), Arsenic (As), Cadmium (Cd), Chromium (Cr), Cobalt (Co), Copper (Cu), Manganese (Mn), Mercury (Hg), Nickel (Ni), Lead (Pb), Thallium (Ti), Vanadium (V).
PolyChloroBiphenils (PCB) are aromatic chlorine compounds belonging to a family of 209 compounds. As they are highly lipophilic and resistant to hydrolysis, acids and basis, and heat, they are non-metabolisable persistent organic substances. PCBs behavior in the environment and their effects on human beings highly depends on chlorination level of these molecules. The more PCBs are chlorinated, the more lypophilic they are, and the more they tend to accumulate in all compartments of the environment, including human beings on which they will concentrate through the whole trophic network by accumulating on all adipose tissues thanks to their lipophylic power. 7 fellow PCBs represent a whole part of PCBs molecules in animal food. They are named as indicator PCBs or PCBi. They are those researched in priority by laboratories.
General formula of PCBs
Dioxins and furans are derivatives from PCBs. It exists 210 dioxins/furans but only 17 are considered as toxic and commonly researched by laboratories.
General formula of dioxins or polychlorodibenzo-para-dioxins (PCDD)
General formula of furans or polychlorodibenzofurans (PCDF)
PAHs are molecules made of carbon and hydrogen atoms constituting at least two condensed aromatic cycles. The most toxic such as Benzo(a)pyren are those researched in priority. Following their nature and origin, PAHs are present in the environment under variable concentrations and more or less complex combinations. Their solubility in water is often low or very low. This hydrophobic characteristic gives these organic molecules the property to be easily adsorbed in grounds and sediments. PAHs have also a high potential of bioconcentration in organisms, in particular those populating aquatic ecosystems. Most of these molecules are then persistent in the environment.
Other examples of PAHs that can be researched: fluoranthene, chrysene, benzo(a)anthracene, etc.
Particles or « dusts» are classified depending their size : « coarse particles » or « PM10 », with a size below 10 µm, and « fine particles» or « PM2,5 », with a size below 2,5 µm.
Their emissions in the environment can be natural or anthropogenic, in particular with road traffic, fuel oil combustion, wood burnout and energy transformation.
Pesticides are the whole chemical products intending to protect cultivated plants from diseases and insects (insecticides, fungicides, etc.). They are several types. For example, deltamethrin (pyrethroid family) is used as an active matter for the making of insecticides for agricultural, veterinary and domestic use. In France, crops treated with deltamethrin are: cereals, vineyards, arboriculture, vegetables and potatoes.
Other examples of pesticides to be researched: lindane, endosulfan, tau-fluvalinate, malathion, etc.
Chemical formula of deltamethrin
They are chemical elements with natural and artificial radioactivity. Radionuclides can be found under natural state or can be artificially produced and obtained after bombardment of stable atomic nucleus by particle rays. While they disintegrate, nucleus will produce either an electromagnetic radiation (gamma or X rays), or a radiation of particles (alpha and electron particles), or both in the same time.
Possible measures of radioactivity: measure of global radioactivity level or research of specific radionuclides (carbon 14 ( 14 C), tritium ( 3 H) etc.).
New emerging pollutants can be defined as non-regulatory compounds. Most of the time they are in the environment since a long time, but their effects have not been sufficiently studied yet. These molecules are good applicants for a potential regulation depending on new data about their effects on health and their persistence in the whole compartments of the environment.
The European network of reference laboratories, research centers and related organizations for monitoring of emerging environmental substances (NORMAN) established a list of those compounds, regularly updated. We can find diverse substances such as products used in industry (pharmaceutical, cosmetic, food-processing, etc.), pesticides, fire retardants, nanoparticles, etc. For example we can talk about the bisphenol A, potential endocrinal disruptors, highly used in plastic industry and recently put on the center stage.
Bisphenol A chemical formula