Organohalogen compounds

The organohalogen compounds (OHCs) regulated under Stockholm Convention on Persistent Organic Pollutants (POPs) were analyzed in the cats’ serum, in the same pools as the BFRs were analyzed. These lipophilic compounds have been regulated for decades but can be found everywhere in the environment and has entered the food web. We (humans and animals) are mainly exposed to these compounds via the food we are eating. Only very low levels could be detected in the household dust.

Figure 1. Organohalogen compounds analyzed in  cats blood, from 17 households. The blood serum was pooled for the household with several cats, except for two cats in household 9 and 17 and reported on gram lipid weight (ng/g lw).

DDT/DDE – The pesticide DDT (dichlorodiphenyltrichloroethane) has been widely discussed mainly due to it’s harmful effects on the wildlife. Rachel Carson wrote the book “Silent Spring” where she described observations based on the, in her view, logic consequences of spreading the pesticide in such an excessive amount all over the environment. Birds were almost extinguished in areas were application were intense, Grey seal in the Baltic Sea got reproductive disturbances and the eggs of the Sea Eagles cracked before hatching. DDT saved millions of lives though, fighting malaria and other vector–borne diseases, and is still allowed to be used in certain areas. DDE (dichlorodiphenyldichloroethylene) is the metabolite (degradation products) formed in biota.

PCBs – The polychlorinated biphenyls are known carcinogens, endocrine disruptors and neurotoxins. The number of chlorines, and positions on the biphenyl are different between the so-called congeners, making it possible to form 209 different congeners. These are numbered 1-209 with increasing chlorines. The PCBs and CB-138 and CB-153 have six chlorines and are two of the most commonly found in biota.

PCP – Pentachlorophenol is a pesticide that has been widely used in Sweden as wood preservative. Its use has been significantly declined, due to the high toxicity and slow biodegradation. It was added to the SC POP list in 2015. PCP is an endocrine disruptor and carcinogen, and can cause neurological effects. It has been reported that it is mainly people working with the chemical that could suffer damages due to acute toxicity.

The levels of the OHCs found in cat serum are typical for what we find in humans and animals. Higher levels of e.g. the pesticides can be found in areas where they have been applied in higher amounts than in Sweden. PCB levels are commonly found at higher levels in countries were the PCB oil hasn’t been taken care of yet, commonly being old transformation stations still leaking out into the environment, or old industries causing historical pollutions.


The results of the OHC analysis are reported together with the BFR data in Norrgran Engdahl et al. 2017 and in Jessica Norrgran Engdahls Thesis 2015.