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ORIGINAL RESEARCH
published: 27 April 2016
doi: 10.3389/fphar.2016.00108
Frontiers in Pharmacology | www.frontiersin.org 1April 2016 | Volume 7 | Article 108
Edited by:
Adolfo Andrade-Cetto,
Universidad Nacional Autónoma de
México, Mexico
Reviewed by:
Jürg Gertsch,
University of Bern, Switzerland
Ashwell Rungano Ndhlala,
Agricultural Research Council,
South Africa
Ildikó Rácz,
University of Bonn, Germany
*Correspondence:
Arno Hazekamp
a.hazekamp@bedrocan.nl
Specialty section:
This article was submitted to
Ethnopharmacology,
a section of the journal
Frontiers in Pharmacology
Received: 25 January 2016
Accepted: 11 April 2016
Published: 27 April 2016
Citation:
Hazekamp A (2016) Evaluating the
Effects of Gamma-Irradiation for
Decontamination of Medicinal
Cannabis. Front. Pharmacol. 7:108.
doi: 10.3389/fphar.2016.00108
Evaluating the Effects of
Gamma-Irradiation for
Decontamination of Medicinal
Cannabis
Arno Hazekamp *
Head of Research and Education, Bedrocan International BV, Veendam, Netherlands
In several countries with a National medicinal cannabis program, pharmaceutical
regulations specify that herbal cannabis products must adhere to strict safety standards
regarding microbial contamination. Treatment by gamma irradiation currently seems the
only method available to meet these requirements. We evaluated the effects of irradiation
treatment of four different cannabis varieties covering different chemical compositions.
Samples were compared before and after standard gamma-irradiation treatment by
performing quantitative UPLC analysis of major cannabinoids, as well as qualitative
GC analysis of full cannabinoid and terpene profiles. In addition, water content and
microscopic appearance of the cannabis flowers was evaluated. This study found that
treatment did not cause changes in the content of THC and CBD, generally considered as
the most important therapeutically active components of medicinal cannabis. Likewise,
the water content and the microscopic structure of the dried cannabis flowers were not
altered by standard irradiation protocol in the cannabis varieties studied. The effect of
gamma-irradiation was limited to a reduction of some terpenes present in the cannabis,
but keeping the terpene profile qualitatively the same. Based on the results presented
in this report, gamma irradiation of herbal cannabis remains the recommended method
of decontamination, at least until other more generally accepted methods have been
developed and validated.
Keywords: medicinal cannabis, cannabinoids, terpenes, gamma-irradiation, quality control
INTRODUCTION
Because medicinal cannabis is often used by chronically ill patients affected by a weakened immune
system, pharmaceutical regulations in countries such as The Netherlands and Canada specify that
these products must adhere to strict safety standards regarding microbial contamination. When
harmful microbes or fungal spores are inhaled during e.g., vaporizing or smoking, they may directly
enter the bloodstream and cause opportunistic infections. Such contamination risks are not merely
hypothetical: cases of chronic pulmonary aspergillosis associated with smoking unsafe cannabis are
well established in the scientific literature (Llamas et al., 1978; Sutton et al., 1986; Marks et al., 1996;
Szyper-Kravitz et al., 2001; Kouevidjin et al., 2003; Cescon et al., 2008; Bal et al., 2010; Ruchlemer
et al., 2015). For those with compromised immune systems, such lung diseases could be even fatal
(Hamadeh et al., 1988).
Hazekamp Effects of Gamma-Irradiation on Medicinal Cannabis
To minimize contamination risks to patients, Dutch
regulations demand that medicinal cannabis contains no more
than 100 colony-forming units (CFUs) per gram of final product,
which is close to sterility1. Under the Canadian program, limits
are somewhat higher with a maximum of 1.000 CFUs per gram2.
Following European or US Pharmacopoeia standards for inhaled
preparations, certain specific pathogens must be completely
absent, i.e., Staphylococcus aureus,Pseudomonas aeruginosa,
and any bile-tolerant Gram-negative bacteria such as E. coli
(EP, 2015; USP, 2015). Furthermore, the absence of fungal
mycotoxins must be confirmed by additional quality control
testing.
Decontamination of medicinal (herbal) cannabis is a
necessity, as it has yet not been possible to grow cannabis plants
under sufficiently sterile conditions to keep contamination
levels below the required safety limits. Even if this were feasible,
the multiple steps involved in harvesting, drying, processing
and packaging cannabis buds would make it extremely hard
to maintain near-sterile conditions throughout the entire
production procedure. As a result, medicinal cannabis in The
Netherlands as well as in Canada is treated by gamma irradiation
before it becomes available to patients1,2.
Methods of Decontamination
Reduction of microbes can be achieved by various treatments, as
listed in Table 1. The optimal choice of decontamination depends
on the nature of the product to be treated. For herbal materials
such as cannabis, the only currently viable option for treatment is
the use of ionizing radiation. Any of the other decontamination
treatments would either affect chemical content or texture (i.e.,
heat, chemicals, pressure, steam; Ruchlemer et al., 2015) or would
not penetrate beyond the surface of the dense cannabis flowers
(i.e., UV-light).
Gamma irradiation involves exposing the target material to
packets of light (photons) that are so highly energetic (gamma
rays) that they damage the DNA strands present in microbes. As
a result, the affected microbes cannot multiply, and consequently
they will perish3. Because medicinal cannabis is a harvested and
dried (i.e., non-living) product, this effect is not relevant for the
condition of the cannabis plant cells.
Irradiation Safety and Concerns
Most commonly, the radioactive element cobalt-60 (60Co) is
used as the source for gamma irradiation. If administered at
appropriate levels, irradiation can be used for the removal of
decay-causing bacteria from many foods and herbs, and can
prevent sprouting of fruit and vegetables to maintain freshness
and flavor (EFSA Panel on Food Contact Materials Enzymes
Flavourings Processing Aids-CEF, 2011; Arvanitoyannis et al.,
2009). Decontamination or sterilization by gamma irradiation
is also widely applied to medical instruments and medicines
(Hasanain et al., 2014).
1https://www.cannabisbureau.nl/english/specication-sheets
2http://www.hc-sc.gc.ca/dhp- mps/marihuana/info/techni-eng.php
3http://www.cdc.gov/nczved/divisions/dfbmd/diseases/irradiation_food/#affect_
foods
TABLE 1 | List of current main methods available for decontamination or
sterilization of (food) products.
Type of decontamination Main treatments
Heat: Dry heat
Steam (autoclave)
Chemicals: Gas (ethylene oxide, ozone, nitrogen dioxide)
Liquid (hydrogen peroxide, formaldehyde)
High pressure: Pascalization
Filtration: Micropore filter (NB: for liquids only)
Radiation: Non-ionizing (UV-light)
Ionizing (gamma-irradiation, X-rays, electron beam)
Over the years, the safety of irradiated foods has been
confirmed in various animal as well as human studies. These
include animal feeding studies lasting for several generations
in several different species, including mice, rats and dogs
(WHO, 1999; EFSA Panel on Food Contact Materials Enzymes
Flavourings Processing Aids-CEF, 2011). NASA astronauts have
been eating irradiated foods when they fly in space since the
1970s (Perchonok and Bourland, 2002). Irradiation-induced
changes in food components are generally small and not
significantly different from those reported in other conventional
preservation processes, especially those based on thermal
treatment (EFSA Panel on Food Contact Materials Enzymes
Flavourings Processing Aids-CEF, 2011; Shahbaz et al., 2015).
The changes in some components that are sensitive to irradiation,
like some vitamins or micronutrients (Caulfield et al., 2008) may
be minimized by using proper treatment conditions (Kilcast,
1994; WHO, 1999).
The safety of irradiated foods has been endorsed by the
World Health Organization (WHO), the Food and Agriculture
Organization of the United Nations (FAO), the U.S. Department
of Agriculture (USDA), Health Canada (HC), the European
Union (EU), and the Food and Drug Administration (FDA).
Gamma irradiation is now permitted by over 60 countries with
at least 400,000 metric tons of foodstuffs annually processed
worldwide (EFSA Panel on Food Contact Materials Enzymes
Flavourings Processing Aids-CEF, 2011). The regulations that
dictate how food is to be irradiated, as well as which foods
are allowed to be treated, may vary greatly from country to
country4.
Despite these developments, irradiation remains a somewhat
controversial decontamination technique that can spark
emotional debates among the general public. One specific
concern with irradiation treatment is the formation of radiolytic
compounds, in particular 2-alkylcyclobutanones (2-ACBs).
These chemicals are formed in minute quantities when high
fat containing foods (such as sesame seeds, pork meat, cheese,
eggs, fish) are subjected to gamma irradiation, and their content
increases with irradiation dose (Zanardi et al., 2007; Lee et al.,
2008). Although some contradictory in vitro findings exist on
the safety of these compounds, overall scientific consensus is that
2-ACBs are not an immediate cause for concern (EFSA Panel
4https://nucleus.iaea.org/ifa/
Frontiers in Pharmacology | www.frontiersin.org 2April 2016 | Volume 7 | Article 108
Hazekamp Effects of Gamma-Irradiation on Medicinal Cannabis
on Food Contact Materials Enzymes Flavourings Processing
Aids-CEF, 2011).
Of course, consumers may also be concerned about the
indirect effects of irradiation, such as the way it changes
the way we relate to food or herbal medicine, or how the
use of radioactive materials affect the environment during
their mining, shipping and use. Furthermore, irradiation,
like any form of treatment, adds to the final cost of a
food product or medicine. All these concerns should be
taken into consideration when determining whether gamma
irradiation is the proper choice for decontamination of a
product.
Evaluating the Effects of Gamma
Irradiation on Medicinal Cannabis
Patients have occasionally expressed their concerns about the
effects of irradiation treatment on medicinal cannabis. Some
have claimed a change of taste or effect, while others worry
about changes in the chemical composition or the quality of
their medicine5. In response to such concerns, some Canadian
licensed producers of medicinal cannabis initially pledged not
to apply irradiation, but were forced to reconsider when their
products could not meet microbial safety requirements. To
cushion the impact on their customers, the obscuring term “cold
pasteurization” was introduced when in fact gamma irradiation
treatment was applied6.
In fresh Cilantro leaves, gamma irradiation was shown to
reduce the content of terpenes such as myrcene and linalool (Fan
and Sokorai, 2002). Likewise, irradiation may perhaps have an
effect on cannabis terpenes, which seem to play an important
role in the synergistic effect and bioavailability of cannabinoids
(Russo, 2011). Although an early study by our group on
the effect of cannabis irradiation did not indicate changes in
the cannabinoid profile (unpublished data), chromatographic
analysis of cannabinoids has significantly improved over the
years meaning that more detailed changes in the cannabinoid
profile may now be visualized. The occurrence of 2-ACBs
seems of limited relevance in the case of cannabis, because
average daily cannabis consumption is very small compared to
other irradiated products such as meats, fruits of vegetables.
Also, cannabis flowers do not contain significant amounts
of fat needed to form these radiolytic compounds in the
first place.
To address the concerns that may exist around gamma
irradiation of medicinal cannabis, we evaluated the effects of
irradiation treatment of four different cannabis varieties covering
different compositions (THC vs. CBD dominant types, Sativa
vs. Indica types). Samples were compared before and right
after standard gamma-irradiation treatment, by performing
quantitative analysis of major cannabinoids, as well as qualitative
analysis of full cannabinoid and terpene profiles. In addition,
water content and microscopic appearance of the cannabis
flowers was evaluated.
5http://www.hc-sc.gc.ca/fn- an/securit/irridation/cyclobutanone-eng.php
6http://www.leafscience.com/2014/05/01/tweeds-first- marijuana-orders-
delayed-irradiated/
MATERIALS AND METHODS
Solvents and Chemicals
All organic solvents were HPLC or analytical grade. Acetonitrile
was obtained from Boom labs BV (Meppel, The Netherlands).
Ethanol and phosphorus pentoxide (P4O10) was purchased from
VWR (Amsterdam, The Netherlands).
Cannabis Samples
Pharmaceutical-grade cannabis was obtained from the licensed
Dutch cultivator, Bedrocan BV (Veendam, the Netherlands).
Plants were grown from genetically identical clones under
standardized indoor conditions. Flower tops were harvested
and air-dried for 1 week under controlled temperature and
humidity. Four different standardized varieties available in
Dutch pharmacies were used for this study i.e., Bedrocan R
,
Bediol R
,Bedica R
, and Bedrolite R
. Batch information
and chemical composition of these products is listed in
Table 2.
All cannabis batches used for this study were harvested in the
period of late 2014–early 2015. Following standard procedure,
each batch was packaged in portions of 250 grams in triple
laminate foil bags with zip-lock closure (type Lamizip aluminum;
Daklapack, The Netherlands) for gamma irradiation treatment
at Synergy Health (Etten-Leur, The Netherlands). Each batch
received an irradiation dose of (minimum) 10 kGy produced with
a Cobalt-60 radiation source.
Of each cannabis variety a 10 gram sample was collected
before (non-irradiated control) as well as after (irradiated
sample) gamma irradiation, resulting in a total of 8 samples for
this study [4 varieties ×2 treatments (before/after irradiation)].
Samples were homogenized by grinding in a blender until the
material was about 5 mm in diameter. Ground samples were
finally used for determination of water content, and for sample
extraction for GC/UPLC analysis. Of variety Bedrocan, the
most popular variety used by Dutch patients (Hazekamp and
Heerdink, 2013), some non-homogenized samples were kept for
microscopic analysis.
All samples were handled and stored under equivalent
conditions. For each variety, irradiated and control samples
were extracted and analyzed on the same day, so that any
changes in chemical composition could only be attributed
to the irradiation treatment. This study was carried out
under a cannabis research license issued by the Dutch Health
Department.
TABLE 2 | Cannabis type and batch information of the cannabis varieties
used in this study.
Variety name Batch # THC/CBD
type
Sativa/Indica
type
Harvest date
Bedrocan A1.01.45 THC Sativa 11-12-2014
Bediol A2.05.15 THC +
CBD
Sativa 25-12-2014
Bedrolite A2.08.13 CBD Sativa 08-01-2015
Bedica A2.07.20 THC Indica 22-01-2015
Frontiers in Pharmacology | www.frontiersin.org 3April 2016 | Volume 7 | Article 108
Hazekamp Effects of Gamma-Irradiation on Medicinal Cannabis
FIGURE 1 | Structures of the cannabinoids quantitatively analyzed by UPLC.
Water Content Determination
Water content of each homogenized sample was determined
by using the Loss on Drying (LOD) method according
to EP monograph 2.3.32 (method C). In short, 500 mg of
each sample (in duplicate) was accurately weighed in small
plastic containers, and dried for 24 h at 40◦C under vacuum
inside a desiccator containing the potent desiccant phosphorus
pentoxide. Subsequently, all samples were weighed again. Water
content (in percentage of initial weight) was determined by
comparing weight before and after the procedure.
Sample Extraction
Ground cannabis samples were extracted for Gas
Chromatography (GC) and Ultra-Performance Liquid
Chromatography (UPLC) analysis as described in the
Dutch Analvtical Monograph for release testing of Cannabis
Flos, version 7.1 (OMC, 2015)7. In short, 1000 mg of each
7https://www.cannabisbureau.nl/medicinale-cannabis-artsen-en-apothekers-
specificaties-en- analysevoorschriften
homogenized sample (in duplicate) was extracted with 40 mL
of absolute ethanol in plastic serum tubes (maximum content
50 mL) while mechanically shaking for 15 min at 300 rpm.
Tubes were then centrifuged at 3000 rpm and clear supernatant
was transferred to a 100 mL volumetric flask. For exhaustive
extraction, the procedure was repeated twice more with 25 mL
of ethanol, and supernatants were combined. Volumes were
adjusted to 100 mL with ethanol, mixed well, and filtered through
a 0.45 µm PTFE syringe filter to remove small particles. Filtrated
extracts were used directly for GC analysis, or further diluted
with acetonitrile/water (70:30, v/v) for analysis by UPLC.
Quantitative UPLC Analysis of Major
Cannabinoids
The UPLC profiles were acquired on a Waters (Milford, MA)
Acquity UPLC system consisting of a gradient pump, an
autosampler, a column oven and a diode array detector (DAD).
The device was controlled by Waters Empower software. Full
spectra were recorded in the range of 200–400 nm. The analytical
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Hazekamp Effects of Gamma-Irradiation on Medicinal Cannabis
FIGURE 2 | Total THC and total CBD content (in % of dry weight) as determined by UPLC analysis, as well as water content (in % of total weight) as
determined by Loss on Drying method (LOD) in all studied varieties before (gray bars) and after (black bars) irradiation treatment.
column was a Waters Aquity C18 (1.7 µm, 2.1 ×150 mm)
equipped with a matching guard column. The mobile phase
consisted of a gradient of acetonitrile (A) and water (B), both
containing 0.1% formic acid. The gradient was programmed as
follows: 0–6 min (hold at 70% A); 6–10.5 min (linear increase to
100% A); 10.5–11 min (hold at 100% A). The column was then
re-equilibrated under initial conditions for 1.5 min, resulting in a
total runtime was 12.5 min. Flow-rate was 0.4 mL/min. Injection
volume was 10 µL. Chromatographic peaks were recorded at
228 nm. All determinations were carried out at 30◦C. All samples
were analyzed in duplicate.
Applying the standard protocol for release testing of medicinal
cannabis (OMC, 2015)7, the following cannabinoids were
quantitatively determined: THC, THCA, CBD, CBDA, delta-8-
THC, CBN. The structures of these compounds, including their
full chemical names, are shown in Figure 1.
Qualitative GC Analysis of Cannabinoid
and Terpene Profiles
Gas chromatography was used for the simultaneous qualitative
analysis of monoterpenes, sesquiterpenes, and cannabinoids
as previously reported (Hazekamp and Fischedick, 2012). An
Agilent GC 6890 series (Agilent Technologies Inc., Santa Clara,
CA, USA) equipped with a 7683 autosampler and a flame
ionization detector (FID) was used. The instrument was equipped
with a DB5 capillary column (30 m length, 0.25 mm internal
diameter, film thickness 0.25 µm; J&W Scientific Inc., Folsom,
CA, USA). The injector temperature was 230◦C, with an injection
volume of 1 µl, a split ratio of 1:20 and a carrier gas (N2) flow
rate of 1.2 ml/min. The temperature gradient started at 60◦C and
linearly increased at a rate of 3◦C/min until the final temperature
of 240◦C which was held for 5 min resulting in a total run time of
65 min/sample. The FID detector temperature was set to 250◦C.
The device was controlled by Agilent GC Chemstation software
version B.04.01.
Microscopic Visualization of Glandular
Hairs
In order to visualize potential morphological changes in
the glandular hairs (where cannabinoids and terpenes are
produced) present in the cannabis flowers, microscopic
analysis of cannabis variety Bedrocan was performed before
and after gamma-irradiation treatment. Whole cannabis
flowers were used, without homogenizing. A Leica (type
MZ16FA) stereo-microscope was used. Images were captured
at a magnification factor ranging from 20 to 120 times
with a Leica (type DFC420C) camera, controlled by LAS
software.
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Hazekamp Effects of Gamma-Irradiation on Medicinal Cannabis
FIGURE 3 | Continued
RESULTS
Loss on Drying
Inhalation, either by smoking or vaporizing, is currently the main
mode of administration used by patients (Hazekamp et al., 2013).
Water content (humidity) seems to have significant impact on
how consumers appreciate medicinal cannabis products during
inhalation (Ware et al., 2006). Although gamma irradiation does
not significantly heat up the treated product, water may be lost
during the procedure either as a result of the irradiation itself
(Yu and Wang, 2007) or because of shipping and handling
of the product during the treatment. Release specifications for
Bedrocan products require the water content to be no more
than 10%. As shown in Figure 2, the actual water content of the
analyzed varieties ranged between 5 and 8%, with no differences
between treated and control samples.
UPLC Analysis
Six major cannabinoids were quantitatively analyzed by applying
a validated UPLC methodology that is used as standard
procedure for release testing of medicinal cannabis in The
Netherlands. As customary, the sum of THC and its acidic
precursor THCA is reported as “total THC content.” Similarly,
the sum of CBD and CBDA is reported as “total CBD content.”
It should be noted that delta-8-THC and CBN are not originally
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Hazekamp Effects of Gamma-Irradiation on Medicinal Cannabis
FIGURE 3 | Continued
produced by the cannabis plant, but are formed as degradation
products of THC by exposure to heat or light, or by prolonged
storage (Hazekamp et al., 2010).
Results of cannabinoid testing are shown in Figure 2,
indicating that levels of total THC and/or CBD were not altered
by irradiation treatment in any of the varieties studied. No delta-
8-THC or CBN was detected in any of the samples (before or
after irradiation) at levels over 0.1% (which equals 1 mg/gram of
cannabis flower).
GC Analysis
Components visualized by GC analysis were not individually
quantified because of the multitude of chromatographic peaks
of interest (>50). Instead, the entire profiles of all visible
peaks are presented in Figure 3. Because of the complexity of
these profiles, the sections of the profile where monoterpenes,
sesquiterpenes, and cannabinoids elute are displayed separately.
For each variety, control (non-irradiated) samples, and treated
(irradiated) samples are shown side by side, using the same
vertical scale to allow direct comparison. The main peaks in
each variety were identified based on previously published data
(Hazekamp and Fischedick, 2012).
While the overall qualitative composition of the samples
was unaltered, differences in several terpene components could
be detected after irradiation in the cannabis varieties studied.
Components that showed a clear reduction after irradiation
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Hazekamp Effects of Gamma-Irradiation on Medicinal Cannabis
FIGURE 3 | Continued
treatment are indicated in Figure 3 by showing the relative
change (in %) compared to untreated sample. Because a small
variability of terpene content between samples is to be expected,
and is also observed between replicates of non-treated samples,
changes that are smaller than +/– 5% are not indicated. The
main components affected were the monoterpenes myrcene,
cis-ocimene and terpinolene, and the sesquiterpenes gamma-
selinene, eudesma-3,7(11)-diene and gamma-selinene. No new
terpene peaks were formed as a result of treatment. No
cannabinoids were altered or formed as a result of irradiation.
Microscopy
Multiple microscopic images were obtained of variety
Bedrocan on flowers collected before and after treatment
with gamma-irradiation, at a magnification of about 20–120
times. The trichomes (glandular hairs) where cannabinoid and
terpenes are excreted by the cannabis plant are clearly visible, as
shown in Figure 4. No clear differences in trichome structure,
color, density, or shape could be observed between the control
(non-irradiated) samples and treated (irradiated) samples.
DISCUSSION AND CONCLUSION
Gamma irradiation treatment of cannabis has become standard
practice in the government-supported medicinal cannabis
programs of The Netherlands as well as Canada. In the study
presented here such treatment, at a radiation dose (10 kGy)
sufficient to reduce microbial contamination (bioburden) to
pharmaceutically acceptable levels, did not cause any changes
in the content of THC and CBD, generally considered as the
most important therapeutically active components of medicinal
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Hazekamp Effects of Gamma-Irradiation on Medicinal Cannabis
FIGURE 3 | GC profiles of four studied varieties showing monoterpenes, sesquiterpenes, and cannabinoids in separate sections. C, control
(non-irradiated); T, treated (irradiated); *: artifact. Numbers indicate percentage of change in treated samples compared to non-treated controls.
cannabis (Grotenhermen and Müller-Vahl, 2012). Likewise, the
water content and the microscopic structure of the dried cannabis
flowers were not altered by standard irradiation protocol in four
different cannabis varieties. The study included representative
varieties of THC and CBD dominant types, as well as Sativa and
Indica types.
In our study, irradiation had a measurable effect on the
content of multiple cannabis terpenes, mainly on the more
volatile monoterpenes. Reduction of affected terpenes was in
general between 10 and 20%, but for some components this
may be as much as 38%. In a previous study evaluating
the effect of gamma irradiation on fresh Cilantro, a decrease
in terpene content was also described (Fan and Sokorai,
2002). However, the authors concluded that the observed loss
of terpenes such as myrcene and linalool was insignificant
compared to the losses that occurred by evaporation during
refrigerated storage of Cilantro. Also in orange juice the effect
of irradiation on terpenes was found to be non-significant
in comparison to changes induced by refrigerated storage
(Fan and Gates, 2001). Likewise, the slight terpene reduction
observed in the current study is comparable to the effect
that short term storage in a paper bag had on cannabis
samples, in a study performed by (Ross and ElSohly, 1996).
A likely explanation therefore seems that gamma irradiation
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Hazekamp Effects of Gamma-Irradiation on Medicinal Cannabis
FIGURE 4 | Microscopic images of trichomes (glandular hairs) before and after treatment with gamma-irradiation. Cannabis variety Bedrocan was used.
Magnification ±20–120 times.
slightly accelerates the evaporation of some of the more volatile
terpenes. This idea is supported by the fact that no degradation
products or additional chromatographic peaks were found to
account for the lost terpenes, with the exception of some
beta-caryophyllene oxide formed in the irradiated sample of
variety Bedica. Interestingly, terpenes were not affected to the
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Hazekamp Effects of Gamma-Irradiation on Medicinal Cannabis
same degree in all varieties, e.g., myrcene content was clearly
reduced in varieties Bedica and Bedrolite but not in variety
Bediol. Perhaps this indicates a protective effect that cannabis
components may have on each other when present in specific
proportions.
Some cannabis users have claimed that irradiation changes
the taste and/or smell of cannabis during smoking or vaporizing
(personal observation by the author). Unfortunately, such
opinions may be hard to substantiate because the same cannabis
is usually not available to consumers in both its irradiated and
non-irradiated form to allow direct comparison, meaning there is
no “base-line” product to quantify the magnitude of the change.
Nevertheless, the taste and smell of cannabis mainly depends
on its terpene (essential oil) content (Russo, 2011). While the
current study indicated quantitative changes in some of the
terpenes upon irradiation, a subtle change in smell or taste may
indeed be possible as a result of such treatment. Despite these
changes, the overall terpene profile of each variety remained
clearly recognizable.
Gamma irradiation remains controversial among some
consumers of medicinal cannabis. However, weighing the risks
vs. the benefits currently keeps pointing toward the use of this
decontamination procedure. After all, cannabis plants cannot
(yet) be grown and processed under conditions aseptic enough
to meet pharmaceutical standards, while infection risks are well
documented in the medical literature and can be harmful or
even fatal to seriously ill patients. Meanwhile, the main harm of
gamma-irradiation seems to be limited to a reduction of some
terpenes present in the cannabis, leading to a small quantitative
effect, but keeping the terpene profile qualitatively essentially
intact.
Based on the results presented in this report, gamma
irradiation of herbal cannabis remains the recommended method
of decontamination, at least until other more generally accepted
methods have been developed and validated. This is especially
important when cannabis is prescribed to seriously ill and
possibly immune-deprived patients, with an increased risk of
suffering from microbial infection. Meanwhile, the development
of improved hygienic standards for cultivation and processing
of medicinal cannabis may ensure that irradiation doses can be
reduced to an absolute minimum. In time, gamma-irradiation
may eventually be replaced with other, more generally accepted,
forms of reliable decontamination.
AUTHOR CONTRIBUTIONS
The author confirms being the sole contributor of this work and
approved it for publication.
ACKNOWLEDGMENTS
The Dutch Office of Medicinal Cannabis (OMC) and
pharmaceutical quality control laboratory Proxy Labs (Leiden,
The Netherlands) are gratefully acknowledged for their support
in performing this study. A big thanks to Gerda Lamers (Leiden
University) for preparing the microscopic images.
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Conflict of Interest Statement: The author is full time employed by Bedrocan BV,
the licensed company that provided the medicinal grade cannabis used for this
study.
Copyright © 2016 Hazekamp. This is an open-access article distributed under the
terms of the Creative Commons Attribution License(CC BY). The use, distribution or
reproduction in other forums is permitted, provided the original author(s) or licensor
are credited and that the original publication in this journal is cited, in accordance
with accepted academic practice. No use, distribution or reproduction is permitted
which does not comply with these terms.
Frontiers in Pharmacology | www.frontiersin.org 12 April 2016 | Volume 7 | Article 108
