Accounts receivable and other, net
Accounts receivable and other, net decreased by $41 million to $2,261 million as at September 30, 2021, compared to $2,302 million as at December 31, 2020. The decrease was primarily due to collections of project billings at our construction operations.
Accounts receivable and other, net decreased by $155 million to $2,302 million as at December 31, 2020, compared to $2,457 million as at December 31, 2019. The decrease was primarily due to the impact of foreign exchange movements at our water and wastewater operations.
Inventory, net
Inventory, net decreased by $125 million to $588 million as at September 30, 2021, compared to $713 million as at December 31, 2020. The decrease was primarily due to fuel deliveries at our nuclear technology services operations.
Inventory, net decreased by $13 million to $713 million as at December 31, 2020, compared to $726 million as at December 31, 2019. The decrease was primarily due to the same factor described above.
Property, plant & equipment (PP&E) and intangible assets
PP&E decreased by $351 million to $3,967 million as at September 30, 2021, compared to $4,318 million as at December 31, 2020. The decrease was primarily due to the amortization of PP&E of $257 million, combined with the impact of foreign exchange of $191 million which is primarily attributable to our healthcare services operations. As at September 30, 2021, PP&E included $403 million of right-of-use assets.
PP&E increased by $251 million to $4,318 million as at December 31, 2020, compared to $4,067 million as at December 31, 2019. The increase was due to foreign exchange movements, primarily at our healthcare services operations, which increased PP&E by $364 million, combined with an increase in the decommissioning liabilities at our nuclear technology services operations. As at December 31, 2020, PP&E included $449 million of right-of-use assets.
Intangible assets decreased by $122 million to $4,243 million as at September 30, 2021, compared to $4,365 million as at December 31, 2020. The decrease was due to amortization expense of $193 million, primarily at our nuclear technology services operations.
Intangible assets decreased by $145 million to $4,365 million as at December 31, 2020, compared to $4,510 million as at December 31, 2019. The decrease was primarily due to amortization expense of $249 million at our nuclear technology services operations, combined with the impact of the sale of the pathology business within our healthcare services operations.
Capital expenditures represent additions to PP&E and certain intangible assets. Included in capital expenditures are maintenance capital expenditures, which are required to sustain the current performance of our operations, and growth capital expenditures, which are made for incrementally new assets that are expected to expand existing operations. Capital expenditures were primarily related to maintenance and improvements on hospital facilities and new hospital equipment at our healthcare services operations and equipment refurbishment, tooling and new fuel design at our nuclear technology services operations. In addition, we include additions to intangible assets in our water and wastewater operations within capital expenditures due to the nature of its concession agreements. Maintenance and growth capital expenditures for the nine months ended September 30, 2021 were $94 million and $430 million, respectively. Maintenance and growth capital expenditures for the year ended December 31, 2020 were $192 million and $241 million, respectively, compared to $123 million and $212 million, respectively, for the year ended December 31, 2019.
Deferred income tax assets
Deferred income tax assets decreased by $4 million to $337 million as at September 30, 2021, compared to $341 million as at December 31, 2020.
Deferred income tax assets increased by $72 million to $341 million as at December 31, 2020, compared to $269 million as at December 31, 2019. The increase in deferred tax assets was driven by tax loss