Accumulation of Heavy Metals in Selected Medicinal Plants - Reviews of Environmental Contamination and Toxicology - page 81

et al. 2004 ). This species absorbs vanadium in leaves up to a level of 339.9 mg/g. In
the past, vanadium compounds were prescribed as therapeutic agents for anemia,
tuberculosis, and diabetes, but recent clinical results show that this element may show
a broad spectrum of toxic effects on the respiratory, circulatory, and central nervous
systems, digestive organs, kidneys, and skin (Venkataraman and Sudha 2005 ).
The utilization of metal-hyperaccumulator medicinal plants in herbal formula-
tions is often risky and may produce imminent metal toxicity to sensitive consum-
ers. Use of metal-contaminated medicinal plants points out the age-old conundrum,
i.e., such plants may offer curative properties to multitudes of people, but metal
contamination of these same plants may pose an ongoing risk to consumers, unless
steps are taken to ensure that the contaminant levels are safe. Considering that mar-
ket demand for herbal drug remedies has increased and will further increase world-
wide, it is essential to reine procedures now used for premarket drug testing to
ensure the quality, eficacy, and safety of such natural remedies. It is our opinion
that sensible and state-of-the-art cultivation collection practices are essential for
plants used in herbal medicines, and only this can provide the basis for appropriate
quality assurance of medicinal plant use. Moreover, we believe the European and
WHO guidelines for raw herbal material collections should be observed by all pur-
veyors of plant medicines (WHO 2003, 2007 ; European Medicines Agency 2006 ).

6 Conclusions

The results of our literature review of heavy metal accumulation in medicinal plants
vs. safe levels lead us to conclude the following:

1. Medicinal plants are prone to contamination from heavy metals.
2. The levels of heavy metals found in medicinal plants reviewed are generally low.
However, excessive and potentially unsafe levels of several metals have appeared
in the 88 species of marketable plant medicine species reviewed: Pb in 21 spe-
cies, Cd in 44 species, and Hg in 10 species.
3. Authorities should establish a more standardized and universally accepted value
for safe levels of heavy metals, metallic minerals or for metal content in medici-
nal plants.
4. Analyses are needed for both end products and raw materials that go to make
phytopharmaceuticals on a priority basis.
5. Steps should be taken to prevent collection and marketing of such medicinal
plants that are prone to heavy metal accumulations.

7 Summary

In this review, we evaluate the reports published between 1993 and 2011 that address
the heavy metal accumulation in 88 medicinal plant species. We compare the safe
limits for heavy metals set by governmental agencies vs. the levels at which such